Allow cubemap face enums to be used by texture functions

Regal has a list of GLenum's accepted by various texture functions for the target parameter and this list does not include the cube map face targets (like GL_TEXTURE_CUBE_MAP_POSITIVE_X).

This change updates this list to include these enums:

> GL_TEXTURE_CUBE_MAP_POSITIVE_X
> GL_TEXTURE_CUBE_MAP_NEGATIVE_X
> GL_TEXTURE_CUBE_MAP_POSITIVE_Y
> GL_TEXTURE_CUBE_MAP_NEGATIVE_Y
> GL_TEXTURE_CUBE_MAP_POSITIVE_Z
> GL_TEXTURE_CUBE_MAP_NEGATIVE_Z

Also includes some updates to .gitignore to filter out all the generated files produced by Visual Studio.