soffice currently fails upon start up at least in GTK case due to
vcl/unx/generic/app/saldisp.cxx SalDisplay ctor calling GetX11SalData()
when the data is actually of type SalGenericData instead.
Add some trivialish first attempts at iOS-specific headers and some
source files that surely are quite bogus and does nothing sane, but
must start with something. Mostly based on the MacOSX ("aqua") code.
