cache by changing the behavior of the query cache resize-method.
- set query_cache_size=<new_size>; is significantly faster than RESET QUERY
  CACHE as it simply destroys and recreates the query cache, whereas
  RESET QUERY CACHE keeps its internal structure aligned with server 
  load profile.


sql/set_var.cc:
  Refactored behavior of function. Instead of setting the global variable
  from within the class method scope we return the new cache size as a 
  result of the method call.
sql/sql_cache.cc:
  - Changed behavior of resize-method. Now, the cache will be cleared as one
    single block of data instead of an iteration over all cached statements.