Yet more changes to create localized builds for Mac

It turns out that we need aliases for all the languages. And more fiddling
when creating the dmg. And a specialized MacPorts build with the install
path as prefix. What this basically means is that our app will be
correctly localized iff run as /Applications/Subsurface.app
Otherwise the gtk default texts (on buttons for example) may or may not be
translated.

One remaining issue is that apparently Gtk's Mac integration triggers on
the untranslated name Help the Menu tree in order to work. Yet we can't
easily tell the app not to translate that word as the translations are
done internally in gtk - we'd basicall have to build special subsurface.mo
files for Mac that don't contain a translation of the word "Help" for this
to work.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

Makefile

@@ -259,7 +259,7 @@ uemis-downloader.o: uemis-downloader.c dive.h uemis.h
 $(OSSUPPORT).o: $(OSSUPPORT).c display-gtk.h
 	$(CC) $(CFLAGS) $(OSSUPPORT_CFLAGS) -c $(OSSUPPORT).c
 
-share/locale/%.UTF-8/LC_MESSAGES/subsurface.mo: po/%.po
+share/locale/%.UTF-8/LC_MESSAGES/subsurface.mo: po/%.po po/%.aliases
 	mkdir -p $(dir $@)
 	msgfmt -c -o $@ po/$*.po
 	@-if test -s po/$*.aliases; then \