comments: Adjust adaptive-fill-prefix to better handle /// comments
comments: Adjust adaptive-fill-prefix to better handle /// comments

Reported-By: da39a3ee5e6b4b0d3255bfef95601890afd80709@protz

FStarLang/fstar-mode.el,FStarLang/fstar-mode.el,FStarLang/fstar-mode.el