Ruby

• dir.c (dir_initialize): use rb_convert_type instead of
  rb_check_convert_type to prevent SEGV by Dir.new(".", true).
  (dir_initialize): use FilePathValue before rb_enc_get(dirname) to
  prevent SEGV by Dir.new(0).

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@18139 b2dd03c8-39d4-4d8f-98ff-823fe69b080e