De-duplicates vtables and enables RTTI on this hierarchy. This is esp. important for exception classes, as RTTI is used to select the catch clause to handle the exception in-flight. The issue is made a bit complicated by the fact that the exception specification changed from C++98 to 11 and that C++98 clients require the empty throw() specification while we don't want to introduce warnings for C++11 users. Let's hope no compiler includes throw specs into the mangled names. Task-number: QTBUG-45582 Change-Id: If086c8c38fccdc2c9c7e2aa7a492192cc1f86a6c Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>