Fix #12723 and simplification and optmization of defaultDisplay helper

(cherry picked from commit a25343001eea2436dcf8ea60deea3844f77e42e4)
Fix memory leaks in tests for css module
No ticket: Improve line-height animation test stability
Correct test assertion of #10227 ticket for IE8
Merge branch '1.x-master' of https://github.com/jquery/jquery into 1.x-master