GL_EXT_provoking_vertex
http://www.opengl.org/registry/specs/gl/EXT/provoking_vertex.txt
GL_EXT_provoking_vertex
	GL_QUADS_FOLLOW_PROVOKING_VERTEX_CONVENTION_EXT 0x8E4C
	GL_FIRST_VERTEX_CONVENTION_EXT 0x8E4D
	GL_LAST_VERTEX_CONVENTION_EXT 0x8E4E
	GL_PROVOKING_VERTEX_EXT 0x8E4F
	void glProvokingVertexEXT (GLenum mode)