cocoa: Avoid deprecated CPS* functions

cocoa: Avoid deprecated CPS* functions

The functions CPSGetCurrentProcess and CPSEnableForegroundOperation
are deprecated in newer versions of MacOSX and cause warning messages
to be logged to the system log. Instead, use the new preferred method
of promoting our console process up to a graphical app with menubar
and Dock icon, which is TransformProcessType. (This function came
in with MacOSX 10.3, so there's no need to retain the old method as
we don't support anything earlier than 10.3 anyway.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andreas Färber <andreas.faerber@web.de>