i965: implement GL_EXT_texture_swizzle

If the texture swizzle is not XYZW (no-op) add an extra MOV instruction
after the TEX instruction to rearrange the components.

src/mesa/drivers/dri/intel/intel_extensions.c

@@ -137,6 +137,7 @@ static const struct dri_extension brw_extensions[] = {
    { "GL_EXT_shadow_funcs",               NULL },
    { "GL_EXT_stencil_two_side",           GL_EXT_stencil_two_side_functions },
    { "GL_EXT_texture_sRGB",		  NULL },
+   { "GL_EXT_texture_swizzle",		  NULL },
    { "GL_EXT_vertex_array_bgra",	  NULL },
    { "GL_ATI_separate_stencil",           GL_ATI_separate_stencil_functions },
    { "GL_ATI_texture_env_combine3",       NULL },