Final set of selected documentation fixes for qtbase
from Qt 4.8 commit bacae725e584f51ee2fd83af7bef3e4515de9587

Task-number: QTBUG-13362
Task-number: QTBUG-18356
Task-number: QTBUG-18417
Task-number: QTBUG-18664
Task-number: QTBUG-21562
Task-number: QTBUG-22094
Task-number: QTBUG-18741
Task-number: QTBUG-15921
Task-number: QTBUG-15738

Change-Id: I3bd33bb7ce7aa991913ba82f3ea0e4b124f3ee41
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>