merge revision(s) 44406: [Backport #9324]

	* 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]


git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/branches/ruby_2_1@44774 b2dd03c8-39d4-4d8f-98ff-823fe69b080e