Remove duplicated function from QCocoaEventDispatcher

Remove duplicated function from QCocoaEventDispatcher

The qt_mac_waitForMoreModalSessionEvents() is identical to
qt_mac_waitForMoreEvents(), except that it passes a different inMode
parameter to [NSApp nextEventMatchingMask]. Change the latter function
to take the mode as a parameter itself, defaulting to the default mode.

Change the dequeue parameter to [NSApp nextEventMatchingMask] from YES
to NO. Having the function dequeue the event, and then immediately
reposting the event is not necessary.

Change-Id: Iba45d41ad3ff4d5721d1068e6d5c78585cb15810
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@nokia.com>