hgweb: show full date in rfc822 format in tooltips at shortlog page

The absolute date was not shown anywhere in the log view for users with
enabled JavaScript.

mercurial/templates/static/mercurial.js

@@ -258,6 +258,7 b' process_dates = (function(document, RegE'
 					// We want both: date + (age)
 					node.textContent += ' ('+agevalue+')';
 				} else {
+					node.title = node.textContent;
 					node.textContent = agevalue;
 				}
 			}