Fix spelling errors in method names in QStorageInfo.

The methods retreiveVolumeInfo() and retreiveDiskFreeSpace() should be
retrieveVolumeInfo() and retrieveDiskFreeSpace().

Task-number: QTBUG-42068
Change-Id: I86137fbff26c42c8cc8bad366a4733118d6ca292
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Build with -no-accessibility on OS X

This build will have broken tool button style. I also do not see a reason why
someone would purposefully leave behind people that could otherwise use their applications.
The build with this flag will be completely unsupported as configure states.

Task-number: QTBUG-32551
Change-Id: Ie33269a49ecc10258c9f8611542f7cf99a698bb5
Reviewed-by: Jan Arve Sæther <jan-arve.saether@theqtcompany.com>