Fix bug calling Dialog.show() while hide() fade-out is in progress, causing Dialog to be added to !DialogLevelManager stack twice.   Fixes #16152 !strict.

git-svn-id: http://svn.dojotoolkit.org/src/dijit/trunk@29836 560b804f-0ae3-0310-86f3-f6aa0a117693
(cherry picked from commit 86e4c01a08c57412a836112d1f50a2ef4f80abe3)
remove CSS correction code for IE8 that wasn't working anyway, fixes #17993

(cherry picked from commit 67a0b5b5004d0b3950183543891cb9c0f24088ea)
(cherry picked from commit 189073dd71b0f4704850ad00b5e034945dc2ccae)