Revert "Merge branch 'master-sec'"

This reverts commit 88cc1688d0cb828c17706b41a8bd27870f2a2beb, reversing
changes made to f049016cd348627bf8db0d72382d7580bf802a79.
* Strip nils from collections on JSON and XML posts. [CVE-2013-0155] * dealing with empty hashes. Thanks Damien Mathieu

Conflicts:
	actionpack/CHANGELOG.md
	actionpack/lib/action_dispatch/http/request.rb
	actionpack/lib/action_dispatch/middleware/params_parser.rb
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/relation/predicate_builder.rb
	activerecord/test/cases/relation/where_test.rb
CVE-2013-0156: Safe XML params parsing. Doesn't allow symbols or yaml.