add position relative to .dropup

docs/assets/css/bootstrap.css

@@ -1790,6 +1790,7 @@ table .span24 {
 .icon-resize-horizontal {
   background-position: -456px -118px;
 }
+.dropup,
 .dropdown {
   position: relative;
 }

less/dropdowns.less

@@ -2,6 +2,7 @@
 // --------------
 
 // Use the .menu class on any <li> element within the topbar or ul.tabs and you'll get some superfancy dropdowns
+.dropup,
 .dropdown {
   position: relative;
 }