More extensions, less bugs

Added GLX_NV_copy_image extension, updated tools

Add compatiblity for some older ffmpeg versions

...I think I need sleep.  That last commit before this one shows it
quite clearly.

Accidentally removed a function from the main module declaration macro.

Instead of doing this, just use macros to handle this situation.

Also, fix a minor bug in AAC encoder

This just adds FFmpeg's default AAC encoder as an audio encoder.  Going
to try to start getting things going with the RTMP output library next.

 - Add interleaving of video/audio packets for outputs that are encoded
   and expect both video and audio data, sorting the packets and sending
   them to the output when both video and audio is received.

 - Combine create and initialize callbacks for the encoder API callback
   interface.

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.