(Man-hyphenated-reference-regexp): New variable.

(Man-hyphenated-reference-regexp): New variable.
(Man-build-references-alist): Use it to search for referenced
manpages.  If hyphenated is non-nil, record a concatenated word in
Man-refpages-alist only if it matches Man-reference-regexp.
Update word's length when it is concatenated.  Reverse the list,
to get the first manpage at the head.
(Man-possibly-hyphenated-word): New function.
(Man-follow-manual-reference): Use it instead of current-word to
find a manpage at point, in a way that accounts for hyphenated
references.