etc.c: Etc namespace

* ext/etc/etc.c (Init_etc): move Passwd and Group under Etc namespace
  as primary names.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40264 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-04-13

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40265 b2dd03c8-39d4-4d8f-98ff-823fe69b080e