Re-enable $wgHtml5
The rendering issue that prompted
r53137 has been fixed in
r53141.
However, everyone should be on the lookout for browsers becoming
slightly more standards-compliant when this is enabled, possibly
breaking some things. Since there are no known issues, it should be
safe to re-enable so it can get further testing. See this page for info
on the effects of different doctypes:
http://hsivonen.iki.fi/doctype/