About page for 3.6.

 * Colorful New Theme
 * Write with Confidence
 * Support for Audio and Video
 * Under the Hood

Screenshots to come. Under the Hood to be finalized and thus not yet offered for translation.

props aaroncampbell, coffee2code, duck_, lessbloat, markjaquith, nacin, samuelsidler, siobhan.
see #24832.



git-svn-id: http://core.svn.wordpress.org/trunk@24802 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Compress scripts/styles: 3.6-RC2-24803.

git-svn-id: http://core.svn.wordpress.org/trunk@24803 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add some missing PHPDoc `@since` lines.

Fixes #24742. Props DrewAPicture.

git-svn-id: http://core.svn.wordpress.org/trunk@24804 1a063a9b-81f0-0310-95a4-ce76da25c4cd