Add QFastMetaBuilder

Add QFastMetaBuilder

This is a faster, but less convenient, version of QMetaObjectBuilder.
The aim is to reduce allocations made during building the meta object
by doing it in two passes - first you reserve all the strings needed
and then you provide their data.

Change-Id: Id9caf9c9c6c2ab6a5219e5cea9363463a4ebf822
Reviewed-on: http://codereview.qt.nokia.com/3763
Reviewed-by: Roberto Raggi <roberto.raggi@nokia.com>