At least OutputDevice::acquire/release use a plain unguarded int and ++, --, so
apparently rely on the SolarMutex being locked whenever they are called.  Fixed
those places that caused "make check" to fail for me when temporarily adding
DBG_TESTSOLARMUTEX() to OutputDevice::acquire/release.  (A recurring pattern is
that a class fails to ensure the SolarMutex is locked around the destruction of
non-null VclPtr members.)

Change-Id: I77cba6f3908f2de1b516ce28f1c3c43b3f57a9c5