GL_AMD_stencil_operation_extended
http://www.opengl.org/registry/specs/gl/AMD/stencil_operation_extended.txt
GL_AMD_stencil_operation_extended
	GL_SET_AMD 0x874A
	GL_REPLACE_VALUE_AMD 0x874B
	GL_STENCIL_OP_VALUE_AMD 0x874C
	GL_STENCIL_BACK_OP_VALUE_AMD 0x874D
	void glStencilOpValueAMD (GLenum face, GLuint value)