paper: fix rendering of the first tab in a line in Webkit (issue3990)

This fixes issue3990 for Webkit-browsers, and also older Opera versions.
Rendering in firefox is not changed.

mercurial/templates/static/style-paper.css

@@ -250,6 +250,7 b' h3 {'
   color: #999;
   text-align: right;
   content: counters(lineno, ".");
+  float: left;
 }
 
 .sourcelines > span:target, tr:target td {