remove .border-radius mixin and replace with standard border-radius property, since -webkit-* and -moz-* are only needed for older versions

less/responsive-navbar.less

@@ -69,13 +69,13 @@
     padding: 9px 15px;
     font-weight: bold;
     color: @navbarLinkColor;
-    .border-radius(3px);
+    border-radius: 3px;
   }
   // Buttons
   .nav-collapse .btn {
     padding: 4px 10px 4px;
     font-weight: normal;
-    .border-radius(4px);
+    border-radius: 4px;
   }
   .nav-collapse .dropdown-menu li + li a {
     margin-bottom: 2px;
@@ -105,7 +105,7 @@
     padding: 0;
     background-color: transparent;
     border: none;
-    .border-radius(0);
+    border-radius: 0;
     .box-shadow(none);
   }
   .nav-collapse .dropdown-menu:before,