Usability fix:

Blender's data link button (typically with menu and searching options)
now has a X icon to clear its contents. 

Before you had to click, delete text, enter.

For example:
- Object Parent
- Modifier objects or vertexgroups

This fix saves each user 100 clicks per day, with 100k users
that's 3 billion clicks per year!

source/blender/editors/interface/interface_layout.c

@@ -1386,7 +1386,7 @@ void ui_but_add_search(uiBut *but, PointerRNA *ptr, PropertyRNA *prop, PointerRN
 
 	/* turn button into search button */
 	if (searchprop) {
-		but->type = SEARCH_MENU;
+		but->type = SEARCH_MENU_UNLINK;
 		but->hardmax = MAX2(but->hardmax, 256.0f);
 		but->rnasearchpoin = *searchptr;
 		but->rnasearchprop = searchprop;