hgweb: remove artificial width constraint from header in monoblue

This width property comes from the beginning of the monoblue theme itself, and
was used to stop the action header ("summary", "shortlog", "changelog", etc)
from clashing with the search form. But it still was happening (on smaller
screens, and with more actions added to hgweb over time).

Effectively, the hardcoded width was preventing the header from fitting into
the available screen space, since it always tried to be 900px wide, even if
that meant horizontal scroll on smaller screens and having the actions on two
lines where one should've been enough. For example,
http://selenic.com/hg/log?style=monoblue has the last two actions ("gz" and
"help") in the header on the second line, even when there seems to be enough
space on the first.

This patch makes the form float, which prevents it from overlaying/clashing
with the action header, and allows the latter to resize itself in the best
possible way.

mercurial/templates/static/style-monoblue.css

@@ -53,10 +53,8 b' div.page-header {'
   }
 
   div.page-header form {
-    position: absolute;
-    margin-bottom: 2px;
-    bottom: 0;
-    right: 20px;
+    float: right;
+    margin-top: -2px;
   }
   div.page-header form label {
     color: #DDD;
@@ -83,7 +81,6 b' div.page-header {'
     margin: 10px 0 0 0;
     list-style-type: none;
     overflow: hidden;
-    width: 900px;
   }
     ul.page-nav li {
       margin: 0 2px 0 0;