Variuos features (native/Qt semaphores/shared memory) are now
configured by macros like USE_QT_SHMEM and USE_QT_SEMAPHORES. This
allows central and individual configuration of features according to
the platform to build for at the beginning of the file.
Finally makes RemotePlugin work on OS X by not using native semaphores
rather than QSystemSemaphore's.
Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>
(cherry picked from commit 2ef5dffec0)