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>