On some operating systems, with specific drivers it seems that BGR/BGRA
isn't properly treated as such in certain cases.  This fix will
hopefully force the formats to be treated as BGR/BGRA when actually
rendering, which should get around the implementation-specific issue.

 - 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.

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

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

Staging surfaces with GL originally copied to a texture and then
downloaded that copied texture, but I realized that there was really no
real need to do that.  Now instead they'll copy directly from the
texture that's given to them rather than copying to a buffer first.

Secondly, hopefully fix the mac issue where the only way to perform an
asynchronous texture download is via FBOs and glReadPixels.  It's a
really dumb issue with macs and the amount of "gotchas" and non-standard
internal GL functionaly on mac is really annoying.

There were a *lot* of warnings, managed to remove most of them.

Also, put warning flags before C_FLAGS and CXX_FLAGS, rather than after,
as -Wall -Wextra was overwriting flags that came before it.

This trick uses FBOs to allow for copying textures without the need for
special texture copy functions.

I removed GLEW, added glLoadGen (renamed to GL here), and added implementations for all platforms. Hopefully this goes better than GLAD did.

 - Removed the dependency on windows.h for windows.  I feel it's an
   unnecessarily large dependency to have to add to all source files
   when the only thing that's needed to make the windows version compile
   the debug functions is just the __stdcall call convention keyword.

   On top of increasing compile time due to the large number of headers
   it includes from all the windows API headers, it also adds a lot of
   potential name conflicts, as I was getting a number of name conflicts
   for lots of names like near/far, which were used in old legacy 16bit
   windows code.

With the permission of my fellow contributors, I'm switching obs-studio back to GPL v2+ to prevent issues between this project and the original OBS project, and for personal reasons to avoid legal ambiguity (not political reasons, I admittedly would prefer GPL v3+)

added VAOs to vertex buffers (might need some future tweaking to check whether buffers are already assigned to specific attributes)

fix up the rest of the GL code, add glew to project, add makefiles for opengl, fix makefiles so that it can be built with gcc, update project files to automatically output to the build directory

update graphics subsystem code to add mipmap support and also add initial GL texture stuff and helper functions