Optimize cleanData: allow direct access to data_priv for cleanup
Fix #13855: line-height animations. Close gh-1265.
Ref 3971c2eb: Sync with 1.x-master
Fix #13835: classes separated by form feed
Fix #13894: CSS identifiers with backslash-escaped whitespace
(cherry picked from commit a75016634d439179fa6517da1918a5a667886e99)