QDialog::setSizeGripEnabled does not disable Mac OS Cocoa resizer

QDialog::setSizeGripEnabled hides the QSizeGrip widget placed in the bottom left of the window, however this does not affect any resize grip displayed by the underlying NSWindow.

QWidgetPrivate::qt_mac_update_sizer disables the NSWindow resizer, however it only does so if:

• The QSizeGrip is present, or
• The window has no frame, or
• The window's min size == the window's max size

This does not handle the case where a QDialog has a frame, hasn't had its min/max clamped, and yet QDialog::setSizeGripEnabled(false) was called.

qt_mac_update_sizer should also see if the widget is a QDialog, and if so always hide the NSWindow resizer (since QDialog will provide one if required).