mesa/swrast: implement EXT_texture_sRGB_decode

This implements the extension by choosing a different set of texture
fetch functions when the texture parameter changes.

Signed-off-by: Dave Airlie <airlied@redhat.com>

src/mesa/main/texobj.c

@@ -141,6 +141,7 @@ _mesa_initialize_texture_object( struct gl_texture_object *obj,
    obj->Swizzle[2] = GL_BLUE;
    obj->Swizzle[3] = GL_ALPHA;
    obj->_Swizzle = SWIZZLE_NOOP;
+   obj->sRGBDecode = GL_DECODE_EXT;
 }