regex.c: Various cosmetic changes

regex.c: Various cosmetic changes

* src/regex-emacs.c (extract_address): New function.
(skip_noops, mutually_exclusive_aux, re_match_2_internal): Use it.
(regex_compile): Fix oversight in last commit.
(analyze_first): Return a bool rather than an int.
(re_compile_fastmap): Simplify accordingly.
(re_match_2_internal): Share the common code between the fail and
success exit paths.