Support MSVC14 and 15 [Bug #11118]

	Search _pioinfo which is not exported after MSVC14.
	[Bug #12014] [GH-884]

	win32.c: suppress warnings

	* win32/win32.c (set_pioinfo_extra): remove "/*" within comment.
	* win32/win32.c (set_pioinfo_extra): use more reliable way to search
	  the position of pioinfo of VC14, and also support debug library of it.
	  patched by davispuh AT gmail.com
	  [ruby-core:76644] [Bug #12644]
	  this fixes also [Bug #12631]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@62884 b2dd03c8-39d4-4d8f-98ff-823fe69b080e