Added it into hasFeature() of all engines which returned `true` in
simpleSaveNames() before.
As mentioned in #788, SCI is not always using simple names, so it
doesn't have such feature now.
Engines with "simple" savenames would support "Run in background" in
save/load dialog and gradual save slots unlocking. Other engines
save/load feature would be locked until save sync is over.
Do not try to read the menu.mor file as it has a different format not
supported (and detection for it was already removed). Also only tries
to read the menu for the original language. This avoids using the
French menu with the German game when both files are present in
the search path.