Use force inlining of YUV conversion functions

Force inling of the 444->420 conversion functions because their CPU
usage goes up pretty heavily without it when compiling without
optimizations
Fix UTF-8 signature detection

The signature detection code when reading UTF-8 files was causing the
UTF-8 strings read from file to allocate more data than they were
supposed to, causing the last 3 bytes to be garbage
Fix FORCE_INLINE macro

Accidentally put the code within a _MSC_VER #ifdef, causing the macro to
not be found on non-VC compilers
Fix __attribute__ usage

Requires two sets of parentheses, not one.  ...I think
Fix a couple of warnings
Implement FBO blit texture copy

This trick uses FBOs to allow for copying textures without the need for
special texture copy functions.
Merge branch 'master' of https://github.com/jp9000/obs-studio
Added initial Mouse pointer lib

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