win32.c: suffix should be alnum
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53705 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
win32.c: suffix should be alnum
suffixes are alpha-numeric only, no needs to scan whole path,
especially path separators.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53705 b2dd03c8-39d4-4d8f-98ff-823fe69b080e