Merge branch 'ab/compat-regex'

* ab/compat-regex:
Fix compat/regex ANSIfication on MinGW
autoconf: regex library detection typofix
autoconf: don't use platform regex if it lacks REG_STARTEND
t/t7008-grep-binary.sh: un-TODO a test that needs REG_STARTEND
compat/regex: get rid of old-style definition
compat/regex: define out variables only used under RE_ENABLE_I18N
Change regerror() declaration from K&R style to ANSI C (C89)
compat/regex: get the gawk regex engine to compile within git
compat/regex: use the regex engine from gawk for compat

Conflicts:
compat/regex/regex.c

diff --cc Makefile
Simple merge

diff --cc config.mak.in
Simple merge

diff --cc configure.ac
Simple merge