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]
merge revision(s) 54737,54740,55792: [Backport #14623]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@62884 b2dd03c8-39d4-4d8f-98ff-823fe69b080e