Merge pull request #5 from dghost/master

Bunch of changes + bug fixes
Renamed r_oculusrift_* to vr_*, shuffled some things around
More renaming
Reset IPD to SDK default
Decoupled libOVR into generic interface; fixed whitespace.
Cleaned up OpenGL extension loading a bit
Sanitized IPD cvar behaviour
Merge branch 'master' of https://github.com/dghost/Quakespasm-Rift

Conflicts:
	Quake/gl_rmain.c
	Quake/gl_rmisc.c
	Quake/vr.c
Renamed most hmd_ prefixes to vr_ where sensible
Allow 0 IPD
Merge branch 'master' of github.com:phoboslab/Quakespasm-Rift