+ when NRCS is active, suppress ISO Latin-1 from menu to avoid
confusion with British NRCS.
+ do not highlight ISO Latin-1 for NRCS, since it is a 96-character
set, not applicable to NRCS.
+ expand menu 11.6.6 to demonstrate bce with top-level menus 1 and 2
in addition to the existing menu 8.
+ correct description for DA response 24; it denotes VT320.
+ add highlighting information for VT320 Portuguese NRC mapping.
+ add highlighting information for VT220 DEC Supplemental NRC mapping.
+ clear screen just before resetting SCS in menu #3 character sets,
in case a VT100 emulator does not simply ignore VT220 G2/G3
selections when it does not implement them.
+ add check for maximum operating level before deciding whether
to send a DECSCL to set it to VT100-level.
+ save/restore color enable-flag for menu 11.6 in a couple of places
so that the ISO-6429 tests do not reset it unexpectedly.
+ amend the REP test to not reset colors if it happens to be run via
the menu entry for BCE-related tests.
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