dir.c: fix escaping multibyte char

	* dir.c (has_magic): fix escaping multibyte char, with glob
  meta-char in trailing bytes, e.g., Shift-JIS

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@49667 b2dd03c8-39d4-4d8f-98ff-823fe69b080e