Texturize: Massive performance improvements (~600% faster); better handling of nbsp, double, and weird spaces; 136 new unit tests.

big props miqrogroove.
fixes #22692.

Built from https://develop.svn.wordpress.org/trunk@27839


git-svn-id: http://core.svn.wordpress.org/trunk@27673 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Fix drag-and-drop upload in distraction-free writing.

props kovshenin.
fixes #27438.

Built from https://develop.svn.wordpress.org/trunk@27840


git-svn-id: http://core.svn.wordpress.org/trunk@27674 1a063a9b-81f0-0310-95a4-ce76da25c4cd