removed duplicated docs in android qsharedmemory and systemsemaphore

removed duplicated docs in android qsharedmemory and systemsemaphore

Qdoc sees all source and header files, rather than the subset selected
by qmake. This leads to qdoc errors when the same functions are
documented in multiple implementations.

In the cases fixed here, all documentation was duplicated, so no
information was lost.

Change-Id: Id7f8e2e617862a3778d0b05b38d8811aad456ac5
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>