Add missing icon class definition for navs.less

add missing icon class definition for navs:
'[class*=" icon-"]'

P.S. Sorry for 2 pull requests with the same problem..

less/navs.less

@@ -67,7 +67,8 @@
   text-shadow: 0 -1px 0 rgba(0,0,0,.2);
   background-color: @linkColor;
 }
-.nav-list [class^="icon-"] {
+.nav-list [class^="icon-"],
+.nav-list [class*=" icon-"] {
   margin-right: 2px;
 }
 // Dividers (basically an hr) within the dropdown