Fix for OS X QFileDialog showing bundle as directory

Also check if the selectedFile is a bundle to correctly
set currentDir.

Patch for Qt 4.8 has been submitted

Task-number: QTBUG-31562

Change-Id: I72b0e8484b3c3a610932c03cd7fdab4ddee70277
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
Cocoa save file dialog behavior fix

Currently, in save mode, if selectFile has not been called, the native
cocoa file dialog puts the folder name in the line edit. This patch
restores the old behavior where the line edit is presented empty to
the user.

Task-number: QTBUG-31619

Change-Id: I938eb6d968e0e2c343e70bc19f29663e112d0496
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>