If you don't need to see what's displayed, then this is particularly
useful for two reasons:
1. It reduces the number of draw/present calls
2. It can prevent issues with certain hardware setups where rendering on
   a monitor hooked up to a separate card can experience slowdowns

Sometimes it can be useful to turn off rendering to the display in order
to reduce the number of draw calls and present calls.

Use std::abs instead of abs to avoid loss in precision and also fix
the corresponding warning from clang (3.5.0):

warning: using integer absolute value function 'abs' when argument is
of floating point type [-Wabsolute-value]

Closes jp9000/obs-studio#414

NixOS installation instructions

Buildfix for older FFmpeg versions (F20 RPMFusion)

The buffer size was being saved as 'VBufsize' while all read operations
tried to read 'Bufsize'

This reverts commit 99c674e4.

These commits were originally added to allow multiple user interfaces to
use the same plugins, but I soon realized that multiple user interfaces
can use multiple libobs versions, so each user interface should have its
own set of plugins to manage.  Some user interfaces may not wish to use
certain plugins anyway, so this fixes that issue as well.

This reverts commit 92d800cc, reversing
changes made to 35a4aced.

These commits were originally added to allow multiple user interfaces to
use the same plugins, but I soon realized that multiple user interfaces
can use multiple libobs versions, so each user interface should have its
own set of plugins to manage.  Some user interfaces may not wish to use
certain plugins anyway, so this fixes that issue as well.

Add $HOME/.obs-plugins as default module search dir on Linux

When display capture is created, the hide_cursor variable is not
initialized, so just initialize it to the setting in the create
function.

The kCGDisplayStreamShowCursor option used with the dictionary does not
work if you assign @true or @false to it.  After some testing, it needs
to point to the id cast of either kCFBooleanTrue or kCFBooleanFalse in
order for it to work properly.

If it doesn't use either of those values, the display stream seems to
use its internal default, which on 10.8 and 10.9 is visible, and 10.10+
is invisible, which would explain why people on 10.10 couldn't get the
cursor to capture.

More advanced ffmpeg output selection

Adds ComboBoxes for selecting format and audio/video
codecs. The ComboBoxes also show only valid codec
combinations for a particular container format.

Allow specification of specific codec ids and container
format to muxing.

the Commodore A64 codecs seem to deref the video frame
too many times causing a crash.  For now just skip if this
codec.

Fixes a crash in formats that don't support both video and audio
streams.

Enable/Disable scale output ComboBox based on whether
the scale checkbox is selected.

This adds utility functions for determining which
codecs and formats are supported by loaded FFMpeg
libraries.  This includes validating the codecs that
a particular format supports.

Added instructions for Ubuntu 15.04
Added JACK2 support in Debian-based distros

FSF address

Some formats (like WMV) would send out audio packets that
had channels set but did not specify a channel layout.
Solution is to no longer rely on channel layout to get the
channels and just get the channel count directly off the
FFmpeg audio frame.

Address for FSF was wrong, corrected

Using Qt to handle crash dialogs is too unstable, so better to just use
the windows API directly and display a windows message box just to be
safe.

I forgot that the track index is 1-based, not 0-bsaed.

All audio encoders are currently having the service-specific settings
applied to them, so this makes it so that it checks which track the
stream is set to and only applies it to that specific encoder.

Instead of manually setting the blend state to the desired values, use
gs_reset_blend_state to ensure we have the default blend state (which
for color is a typical srcalpha/invsrcalpha alpha blending operation,
then the alpha channels are added together).

This fixes an issue where filtered scenes would look strange due to the
fact that alpha was not being blended properly.

This allows the ability to separate the blend states of color and alpha.

The default blend state has also changed so that alpha is always added
together to ensure that the destination image always gets an alpha value
that is actually usable after the operation (for render targets).

Old default state:
  color source: GS_BLEND_SRCALPHA, color dest: GS_BLEND_INVSRCALPHA
  alpha source: GS_BLEND_SRCALPHA, alpha dest: GS_BLEND_INVSRCALPHA

New default state:
  color source: GS_BLEND_SRCALPHA, color dest: GS_BLEND_INVSRCALPHA
  alpha source: GS_BLEND_ONE,      alpha dest: GS_BLEND_ONE

If the cache is freed the current async frame will of course become
invalid, so make sure it's set to null if the cache is freed.

This fixes an issue where cache frames would not free at all after
having been allocated with no upper limit on the cached frame size.  If
cached frames go unused for a specific period of time, they are
deallocated and removed from the cache.

This is preferable to having an upper cache limit due to the potential
for async delay filtering.

This reverts commit 4459ed3e.

Under certain circumstances the cache could be prone to growing too
large unintentionally.  Setting a hard maximum limit should prevent
memory from growing if we suddenly get a lot of frames.