elm_genlist: Added elm_genlist_filtered_items_count API

Summary: This clarifies the documentation of the new api.

Reviewers: SanghyeonLee, shilpasingh, cedric

Reviewed By: cedric

Subscribers: bu5hm4n, buds

Differential Revision: https://phab.enlightenment.org/D3725

legacy/elementary/src/lib/elm_genlist.eo

@@ -426,10 +426,9 @@ class Elm.Genlist (Elm.Layout, Elm.Interface_Scrollable, Evas.Clickable_Interfac
       filtered_items_count @const {
          [[Return how many items have passed the filter currently.
          
-           This behaviour is O(1) and may or may not return the 
-           filtered count for complete genlist based on the timing
-           of the call. To get complete count, call after "filter,done"
-           callback
+           This behaviour is O(1) and returns the count of items which
+           are currently passed by the filter. After "filter,done", the
+           call returns total count of the filtered items.
          ]]
          return: uint;
       }