Synchronize stable/9 Forth code with head via MFC of 22 revisions:
227727, 233941, 235560, 238431, 241310, 241361, 241363, 241365, 241367,
241523, 242667-242669, 242923, 243114, 243660, 244048, 244089, 244158,
253715, 254105, and 254108.

This includes critical fixes that sadly should have been merged prior.
Namely, SVN r244158 fixes a possible regression.