Minor change to the wording. It used to say "files with the prefix 'ubi_'"

Minor change to the wording.  It used to say "files with the prefix 'ubi_'"
or some such.  Some future files won't have the ubi_ prefix.  -)----- Chris
(This used to be commit 955a9f9199b468b72c4b828fed5b2903d0a5273a)