* configure.in: let mingw do something black-magic, and check if
_gmtime64_s() is available actually.
* win32/win32.c (gmtime_s, localtime_s): use _gmtime64_s() and
_localtime64_s() if available, not depending on very confusing
mingw variants macros. based on the patch by phasis68 (Heesob
Park) at [ruby-core:58764]. [ruby-core:58391] [Bug #9119]
merge revision(s) 44406: [Backport #9324]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@44774 b2dd03c8-39d4-4d8f-98ff-823fe69b080e