Remove SetWindowMenuLabelTranslated() which was only called once and so
didn't seem to be worth having. Also get rid of WINDOW_MENU_LABEL for
the same reason: it was used only once and imposed the use of
gettext_noop() which is not needed any longer.
Rename GetWindowMenuLabelTranslated() to have a MSW prefix in order to
indicate that it's a private MSW function and not part of the public wx
API.
Also renamed "Translated" to "Current" to (hopefully) more clearly
indicate why do we need to keep this variable.
2ee322b667