Fix issue with attr_protected where malformed input could circumvent
protection

Fixes: CVE-2013-0276

Conflicts:
	activemodel/lib/active_model/attribute_methods.rb
	activerecord/test/cases/mass_assignment_security_test.rb
fix serialization vulnerability
Merge branch '3-0-sec' into 3-0-stable

* 3-0-sec:
  fix serialization vulnerability
  Fix issue with attr_protected where malformed input could circumvent protection