REGRESSION: For Option+<key> on Mac, event.key in Keys.onPressed is no longer guaranteed to equal <key>

When pressing Option+<key> on the Mac:

• In Qt 4, event.key in Keys.onPressed equals <key>.
• In Qt 5.2, event.key in Keys.onPressed is not guaranteed to equal <key>. Instead, it equals the keycode of the "alternate character" (e.g. Qt.Key_nobreakspace instead of Qt.Key_Space for Option+Space).

This requires platform-specific code for capturing Option+<key> on the Mac (by tracking down the keycode for the alternate character, then adding Mac-specific code to handle it).

More info: http://qt-project.org/forums/viewthread/40920