[Ohrrpgce] SVN: teeemcee/13188 EditorKit: proper, working submenu support; add enter_submenu()

[subversion at HamsterRepublic.com]

teeemcee
2023-04-05 21:07:36 -0700 (Wed, 05 Apr 2023)
288
EditorKit: proper, working submenu support; add enter_submenu()

It was pretty broken. Now it remembers the menu state (cursor) in each submenu,
and the stack of submenus. I can't believe how complex this is. Didn't really
need to use a hash table.

Updated Achievements editor to use it.
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U   wip/editorkit.bas
U   wip/editorkit.bi
U   wip/generaledit.rbas