Allows to drop all the special SVMain handling introduced for
MacOSX. This way LO can also be build via SSH, because gengal
won't abort / fail because of the missing window system.

Currently this just implements the global menu. I don't know
what else is missing. Eventually we want to reimplement the
Cocoa debug option forwarding (NSAccessibilityDebugLogLevel).

Change-Id: I359c46fd03e2436a8a37fd211e59e4e305f8aba0
Reviewed-on: https://gerrit.libreoffice.org/60571
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>