Fix width of search box

docs/source/_static/default.css

@@ -485,6 +485,12 b' span.linkdescr {'
     font-size: 90%;
 }
 
+.search input[name=q] {
+    max-width: 100%;
+    box-sizing: border-box;
+    -moz-box-sizing: border-box;
+}
+
 ul.search {
     margin: 10px 0 0 20px;
     padding: 0;