QtMetaTypePrivate::QAssociativeIterableImpl::{find,begin,end}() allocate a new _iterator,
so when they're used outside of the ref-counted world of QAssociativeIterable::const_iterator,
their lifetime needs to be manually managed.
Instead of going to that length, which failed in previous iterations of this patch, implement
value() in terms of (new) find() and let find() operate on const_iterator.
Because of forwards compatibility between patch releases, use (unexported) friend functions
for now with the intention to make them proper member functions come Qt 5.5.
Task-number: QTBUG-41469
Change-Id: I43b21eae0c2fc4c182369e669a8b3b457be68885
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
d7fa2d060a