GL: Correct texture reswizzling, fix A4R4G4B4.
GL: support the G8B8 tex format.
GL: Add support for R6G5B5.
GL: Correct byteswapping for 565 type textures.
GL: Small simplification.
Typo.
Merge pull request #238 from unknownbrackets/texformats

Correct various texture formats in OpenGL