Use GET for nav menu selection, and default action.

fixes #23813. props helen.

git-svn-id: http://core.svn.wordpress.org/trunk@23807 1a063a9b-81f0-0310-95a4-ce76da25c4cd
RTL for Nav Menu tweaks. see #23641. see #23645. props lessbloat

git-svn-id: http://core.svn.wordpress.org/trunk@23808 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Compress scripts/styles: 3.6-alpha-23809.

git-svn-id: http://core.svn.wordpress.org/trunk@23809 1a063a9b-81f0-0310-95a4-ce76da25c4cd