Use hash_equals() for old md5 hashes.

Merges [30412] to the 3.8 branch.


git-svn-id: https://develop.svn.wordpress.org/branches/3.8@30415 602fd350-edb4-49c9-b593-d223f7449a82
Form validation for password resets.

Merges [30417] to the 3.8 branch.


git-svn-id: https://develop.svn.wordpress.org/branches/3.8@30420 602fd350-edb4-49c9-b593-d223f7449a82