Before this commit, if several menu entries (possibly in different
menus) had the same label after translation and latin1-ization by
FGLocale::utf8toLatin1(), selecting one of them used to fire the
bindings associated to all such entries. This is because the bindings
used to be stored in an std::map whose keys were the
translated-and-latin1-ized labels.
This commit fixes the problem in the following way:
- the std::map (_bindings) is turned into an std::forward_list;
- each element of this std::forward_list references the bindings
assigned to a menu entry;
- in order to allow FGPUIMenuBar::fireItem() to find the bindings
assigned to the menu entry that triggered it,
FGPUIMenuBar::make_menu() calls puMenuBar::add_submenu() with an
additional argument ("user data") that attaches to the puObject for
each menu entry a pointer to the relevant element of _bindings.
Note: given how the menubar is created, an std::vector wouldn't be
appropriate for _bindings, because we need the pointers to its elements
to be stable when new elements are added to _bindings.
Reported by Wayne Bragg: https://sourceforge.net/p/flightgear/mailman/message/37682605/
afe7d996af