Ajax: Remove workaround for IE6/7

Closes gh-1597
Ref #8138
Data: avoid non-alphanumeric chars in expando properties

Ref chromium issue 378607
Ref #14839
Closes gh-1662
Ajax: remove event dependency from the ajax module

Closes gh-1695
CSS: Clean up memory leak in reliableMarginRight

Fixes gh-1795
Closes gh-1893

Thanks for the report flexphperia!