Try not to send Last-Modified, even with an empty value. Some servers interpret an empty value as the epoch.

Props nacin, slene, SergeyBiryukov, andy
see #23021 for trunk


git-svn-id: http://core.svn.wordpress.org/trunk@23267 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Restore TinyMCE dropdowns to their 3.4 appearance in RTL. props helen. see #23101.



git-svn-id: http://core.svn.wordpress.org/trunk@23275 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Taxonomy postbox: fix toggling with "Choose from the most used tags" when several postboxes are shown, props SergeyBiryukov, fixes #23112 for trunk

git-svn-id: http://core.svn.wordpress.org/trunk@23278 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Compress scripts/styles: 3.6-alpha-23279.

git-svn-id: http://core.svn.wordpress.org/trunk@23279 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Don't unnecessarily re-render the attachment details view when editing the title and caption. Re-rendering causes issues with tabbing and focus, and is only necessary for other views (such as "Caption this image..." when editing a gallery).

props koopersmith.
fixes #23054.
for trunk.



git-svn-id: http://core.svn.wordpress.org/trunk@23283 1a063a9b-81f0-0310-95a4-ce76da25c4cd