The function CRM_Core_Invoke::rebuildMenuAndCaches should also flush the memory caches

The function CRM_Core_Invoke::rebuildMenuAndCaches should also flush the memory caches, and hence call: CRM_Utils_System::flushCache( );

This will make things more consistent and actually rebuild all caches as the function name suggests.

(Creating an issue based on http://civicrm.stackexchange.com/questions/2615/how-does-one-flush-the-non-database-cache-such-as-memcache-from-civicrm-code)