+20180630
+ + add acsc string to vi200 (Nibby Nebbulous)
+ add right/down-arrow to vi200's acsc -TD
+ + add "x" to tput's getopt string so that "tput -x clear" works
+ (Nicholas Marriott).
+ + minor fixes prompted by anonymous report on stack overflow:
+ + correct order of checks in _nc_get_locale(), for systems lacking
+ locale support.
+ + add "#error" in a few places to flag unsupported configurations
+