Only accept actions without File::SEPARATOR in the name.

This will avoid directory traversal in implicit render.

Fixes: CVE-2014-0130
Preparing for 3.2.18 release
Fix broken tests of the previous release
Merge branch '3-2-sec' into 3-2-stable

Conflicts:
	actionpack/CHANGELOG.md
Merge pull request #1 from rails/3-2-stable

3.2.18