hgweb: pull line numbers out of main flow of source content

Pulls the autogenerated line number boxes outside of the padding box
of the main content of .sourcelines, allowing the first tab
to be properly sized and the line numbers to be outside
the main source's margin when text is wrapped.

mercurial/templates/static/style-paper.css

@@ -239,8 +239,9 b' h3 {'
 
 .sourcelines > span {
   display: inline-block;
+  box-sizing: border-box;
   width: 100%;
-  padding: 1px 0px;
+  padding: 1px 0px 1px 5em;
   counter-increment: lineno;
 }
 
@@ -251,8 +252,8 b' h3 {'
   -ms-user-select: none;
   user-select: none;
   display: inline-block;
+  margin-left: -5em;
   width: 4em;
-  margin-right: 1em;
   font-size: smaller;
   color: #999;
   text-align: right;