Add preliminary streaming code for testing

 - Add some temporary streaming code using FFmpeg.  FFmpeg itself is not
   very ideal for streaming; lack of direct control of the sockets and
   no framedrop handling means that FFmpeg is definitely not something
   you want to use without wrapper code.  I'd prefer writing my own
   network framework in this particular case just because you give away
   so much control of the network interface.  Wasted an entire day
   trying to go through FFmpeg issues.

   There's just no way FFmpeg should be used for real streaming (at
   least without being patched or submitting some sort of patch, but I'm
   sort of feeling "meh" on that idea)

   I had to end up writing multiple threads just to handle both
   connecting and writing, because av_interleaved_write_frame blocks
   every call, stalling the main encoder thread, and thus also stalling
   draw signals.

 - Add some temporary user interface for streaming settings.  This is
   just temporary for the time being.  It's in the outputs section of
   the basic-mode settings

 - Make it so that dynamic arrays do not free all their data when the
   size just happens to be reduced to 0.  This prevents constant
   reallocation when an array keeps going from 1 item to 0 items.  Also,
   it was bad to become dependent upon that functionality.  You must now
   always explicitly call "free" on it to ensure the data is free, and
   that's how it should be.  Implicit functionality can lead to
   confusion and maintainability issues.
Fix a few warnings
Ensure names are valid

Ensure that a source has a valid name.  Duplicates aren't a big deal
internally, but sources without a name are probably something that
should be avoided.  Made is so that if a source is programmatically
created without a name, it's assigned an index based name.

In the main basic-mode window, made it check to make sure the name was
valid as well.
Ensure URL and key are valid if trying to stream
CoreAudio: fix properties for input/output

Also, check that audio devices are available before setting defaults
Fix minor warning (redundant code)
Allow file names to be used instead of URLs
- added missing header for linux
added linux test module with first implementation of a screengrabber using the xshm extension for x11
Added initial Mouse pointer lib

Added library to get the mouse pointer with the XFixes
extension and draw it via a sprite.
Improved mouse cursor handling

If the mouse pointer changes but has the same size
as before, the texture will be updated.
The mouse pointer is now moved with a matrix function.
Added Blending for mouse pointer
some cleanups

- added some documentation
- removed some debug statements
Moved screen grabber code to _tick function

Moved the screen grabbing and texture generation to the
_tick function in order to keep _render fast
Implemented _tick function in xcursor library

Implemented a _tick function in the xcursor library,
so the cursor texture and position can be updated
from the input plugin _tick function.
Removed unnecessary members from data struct
migrated xshm video source to the new plugin api
added initial pulse audio input plugin

- first try at implementing a pulse audio input plugin,
  it is currently completely untested.

- added license headers to source files
In the API update the diffuse effect got renamed to image.
Removed unnecessary buffer

Instead of copying the data from pulse to a local buffer and
then push it to obs, the pointer from pulse is now used and
pa_stream_drop() called afterwards.