Improve the properties API so that it can actually respond somewhat to
user input.  Maybe later this might be further improved or replaced with
something script-based.

When creating a property, you can now add a callback to that property
that notifies when the property has been changed in the user interface.
Return true if you want the properties to be refreshed, or false if not.
Though now that I think about it I doubt there would ever be a case
where you would have this callback and *not* refresh the properties.

Regardless, this allows functions to change the values of properties or
settings, or enable/disable/hide other property controls from view
dynamically.

1) Fixed the preview window. It now correctly displays the source.
2) The GLX backend now correctly uses the devices current swap.
3) We now set device->cur_swap to a default so we don't have to check it in every function.
4) Minor syntactical cleanups and perhaps some messiness added.

This unfortunately re-introduces undesirable rendering behaviour for
slow renderers (e.g. first gen Intel HD graphics/Apple software
renderer) when the property window is open, but fixes property window
preview rendering for sufficiently fast renderers

Remove unneeded assignment from previous code.

Fix gswindow display with Qt

 - Add start/stop code to obs-output module

 - Use a circular buffer for the buffered encoder packets instead of a
   dynamic array

 - Add pthreads.lib as a dependency to obs-output module on windows in
   visual studio project files

 - Fix an windows export bug for avc parsing functions on windows.
   Also, rename those functions to be more consistent with each other.

 - Make outputs use a single function for encoded data rather than
   multiple functions

 - Add the ability to make 'text' properties be passworded

Several CMake fixes and enhancements

This is mainly intended to be used for preloaded/injected DLLs, which
don't belong into the libdir or plugindir.

 - obs-outputs module:  Add preliminary code to send out data, and add
   an FLV muxer.  This time we don't really need to build the packets
   ourselves, we can just use the FLV muxer and send it directly to
   RTMP_Write and it should automatically parse the entire stream for us
   without us having to do much manual code at all.  We'll see how it
   goes.

 - libobs:  Add AVC NAL packet parsing code

 - libobs/media-io:  Add quick helper functions for audio/video to get
   the width/height/fps/samplerate/etc rather than having to query the
   info structures each time.

 - libobs (obs-output.c):  Change 'connect' signal to 'start' and 'stop'
   signals.  'start' now specifies an error code rather than whether it
   simply failed, that way the client can actually know *why* a failure
   occurred.  Added those error codes to obs-defs.h.

 - libobs:  Add a few functions to duplicate/free encoder packets

Note that this is a somewhat heavily modified custom version of librtmp.
I modified all the platform specific code that we were using for the
OBS1 to make it platform-independent.

I don't really like the code in this library, but it works well enough,
so I can't really fault anyone for it.  It's just very..  unclean.  Even
for a C library, quite unclean.  Some parts are also a little less safe
than I'd prefer as well.

The serializer code is meant to be used as a means of reading/writing
data from any arbitrary type of input/output.

The array output serializer makes it so we can stream data to a dynamic
array on the fly.

Don't clear any data if it's a dummy texture.

 - Add dummy GL texture support to allow libobs texture references to be
   created for GL without

 - Add a texture_getobj function to allow the retrieval of the
   context-specific object, such as the D3D texture pointer, or the
   OpenGL texture object handle.

 - Also cleaned up the export stuff.  I realized it was all totally
   superfluous.  Kind of a dumb moment, but nice to clean it up
   regardless.

 - Make it so that encoders can be assigned to outputs.  If an encoder
   is destroyed, it will automatically remove itself from that output.
   I specifically didn't want to do reference counting because it leaves
   too much potential for unchecked references and it just felt like it
   would be more trouble than it's worth.

 - Add a 'flags' value to the output definition structure.  This lets
   the output specify if it uses video/audio, and whether the output is
   meant to be used with OBS encoders or not.

 - Remove boilerplate code for outputs.  This makes it easier to program
   outputs.  The boilerplate code involved before was mostly just
   involving connecting to the audio/video data streams directly in each
   output plugin.

   Instead of doing that, simply add plugin callback functions for
   receiving video/audio (either encoded or non-encoded, whichever it's
   set to use), and then call obs_output_begin_data_capture and
   obs_output_end_data_capture to automatically handle setting up
   connections to raw or encoded video/audio streams for the plugin.

 - Remove 'active' function from output callbacks, as it's no longer
   really needed now that the libobs output context automatically knows
   when the output is active or not.

 - Make it so that an encoder cannot be destroyed until all data
   connections to the encoder have been removed.

 - Change the 'start' and 'stop' functions in the encoder interface to
   just an 'initialize' callback, which initializes the encoder.

 - Make it so that the encoder must be initialized first before the data
   stream can be started.  The reason why initialization was separated
   from starting the encoder stream was because we need to be able to
   check that the settings used with the encoder *can* be used first.

   This problem was especially annoying if you had both video/audio
   encoding.  Before, you'd have to check the return value from
   obs_encoder_start, and if that second encoder fails, then you
   basically had to stop the first encoder again, making for
   unnecessary boilerplate code whenever starting up two encoders.

This fixes some problems with multiple swap chains (e.g. flickering
between the render views)

Also add support for capturing displays that are not the main display as
preparation for moving the code from test-plugins into a proper plugin
in the future

I neglected to make it initialize the actual control values with the
current settings

 - Add a properties window for sources so that you can now actually edit
   the settings for sources.  Also, display the source by itself in the
   window (Note: not working on mac, and possibly not working on linux).

   When changing the settings for a source, it will call
   obs_source_update on that source when you have modified any values
   automatically.

 - Add a properties 'widget', eventually I want to turn this in to a
   regular nice properties view like you'd see in the designer, but
   right now it just uses a form layout in a QScrollArea with regular
   controls to display the properties.  It's clunky but works for the
   time being.

 - Make it so that swap chains and the main graphics subsystem will
   automatically use at least one backbuffer if none was specified

 - Fix bug where displays weren't added to the main display array

 - Make it so that you can get the properties of a source via the actual
   pointer of a source/encoder/output in addition to being able to look
   up properties via identifier.

 - When registering source types, check for required functions (wasn't
   doing it before).  getheight/getwidth should not be optional if it's
   a video source as well.

 - Add an RAII OBSObj wrapper to obs.hpp for non-reference-counted
   libobs pointers

 - Add an RAII OBSSignal wrapper to obs.hpp for libobs signals to
   automatically disconnect them on destruction

 - Move the "scale and center" calculation in window-basic-main.cpp to
   its own function and in its own source file

 - Add an 'update' callback to WASAPI audio sources

The ones that were being used returned the previous value rather than
the new value

Microsoft's garbage compiler just doesn't even..  read the names of
enums.  It sees an enum and goes "durr, that's an int" without even
properly evaluating it.  Just total garbage, as per usual.

If integers are used, then store as integers.  If doubles are used, then
store as doubles.  This way precision issues are prevented.

Removed some warnings associated with it, was the wrong variable type.

You have to use qt5_use_modules otherwise it just won't always work.  I
don't know how it was working before with cmake, but apparently this
does the trick to ensure that all the necessary libraries and includes
are added.  ..Might require cmake 3.8.9 though.  ..I do hope that
doesn't end up being a problem.

Also, rename atomic functions to be consistent with the rest of the
platform/threading functions, and move atomic functions to threading*
files rather than platform* files

Automatically query defaults for sources/outputs/encoders and set them
before calling create