dir.c: check boundary

* dir.c (glob_make_pattern): check boundary before accessing.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45957 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-05-16

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45958 b2dd03c8-39d4-4d8f-98ff-823fe69b080e