Fully expand entities to ensure deep or widely nested ones fail parsing

With 512a1ce0698d370c313bb561bbf078935fa0342e, we failed when parsing
entities whose partially expanded size was greater than 1024
characters. That was not enough, so now we fully expand all entities.

This is a backport of f1053d94f59f053ce4acad9320df14f1fbe4faac.

Change-Id: I41dd6f4525c63e82fd320a22d19248169627f7e0
Reviewed-by: Richard J. Moore <rich@kde.org>
QObject: use per-thread storage for qFlagLocation()

qFlagLocation() uses a global char* array to transport source location
information from the connect() side to the metaobject side. The size
of the array is 2 (two), which just about suffices for a single connect()
statement.

Obviously, if more than one thread makes a (_any_) connection at the same
time, the data is useless and, worse, there's a data race.

The non-reentrancy of qFlagLocations() cannot and need not be fixed,
but use a per-thread flagged_locations array in QThreadData so threads
don't disturb each other.

Task-number: QTBUG-3680

Change-Id: If1797c60751f551694def69afee6fbe295bbe2d2
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
(cherry picked from qtbase/c012ee2940bc087720b4aa0d257540921cf9a139)
Reviewed-by: Lars Knoll <lars.knoll@digia.com>