features: Support more than 32 features!

Currently features are represented as bits in a 32bit mask so we
obviously can't have more than 32 features with that approach. The new
approach is to use the COGL_FLAGS_ macros which lets us handle bitmasks
without a size limit and we change the public api to accept individual
feature enums instead of a mask. This way there is no limit on the
number of features we can add to Cogl.

Instead of using cogl_features_available() there is a new
cogl_has_feature() function and for checking multiple features there is
cogl_has_features() which takes a zero terminated vararg list of
features.

In addition to being able to check for individual features this also
adds a way to query all the features currently available via
cogl_foreach_feature() which will call a callback for each feature.

Since the new functions take an explicit context pointer there is also
no longer any ambiguity over when users can first start to query
features.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

cogl/cogl-pipeline-layer-state.c

@@ -664,11 +664,13 @@ cogl_pipeline_set_layer_point_sprite_coords_enabled (CoglPipeline *pipeline,
   CoglPipelineLayer           *new;
   CoglPipelineLayer           *authority;
 
+  _COGL_GET_CONTEXT (ctx, FALSE);
+
   g_return_val_if_fail (cogl_is_pipeline (pipeline), FALSE);
 
   /* Don't allow point sprite coordinates to be enabled if the driver
      doesn't support it */
-  if (enable && !cogl_features_available (COGL_FEATURE_POINT_SPRITE))
+  if (enable && !cogl_has_feature (ctx, COGL_FEATURE_ID_POINT_SPRITE))
     {
       if (error)
         {