Eliminated the "Paste Over" option/behavior. Paste (Ctrl-V, F6 or Shift-Insert)

is always the same operation (e.g. Paste-Insert).
MSK_PASTE_OVER and MSK_PASTE_INSERT have been removed (now combined into
MSK_PASTE), so current SCFG code, for example, won't compile.
Introduced a separate WIN_CUT uifc.list mode flag to enable the Cut (e.g.
Ctrl-X) option on the status/help line.
Re-factored the bottomline() routine to re-use the WIN_* mode flags.