implement submenus in user menu (f2)

[jose1711]

the current implementation of user menu only allows a flat structure. i always liked the way how volkov commander did this: vc.mnu held the main configuration similar to mc.menu but it could also reference other .mnu files so one could nest theam easily.

i wish mc had this a similar functionality. it would be nice to be able to do F2 - Edit.. - Edit using vim/nano/mcedit..

[jose1711]

btw norton commander also knew the concept of submenus (plus it also contained an integrated editor). unlike volkov commander the configuration however is kept in a single file (nc.mnu), example:

a: Foo
  foo.exe
b: Submenu1
{
c: do something
  something.exe
d: do something else
  somethingelse.exe
}
c: Submenu2
{
d: undo something
  undo.exe
e: undo something else
  undosomethingelse.exe
}

[jose1711]

example user menu defined in norton commander