GL_EXT_render_snorm
http://www.opengl.org/registry/specs/EXT/render_snorm.txt
GL_EXT_render_snorm

	GL_BYTE 0x1400
	GL_SHORT 0x1402
	GL_R8_SNORM 0x8F94
	GL_RG8_SNORM 0x8F95
	GL_RGBA8_SNORM 0x8F97
	GL_R16_SNORM_EXT 0x8F98
	GL_RG16_SNORM_EXT 0x8F99
	GL_RGBA16_SNORM_EXT 0x8F9B
