renamed default variable in has-layout mixin to more appropriate name…

… $approach

frameworks/compass/stylesheets/compass/utilities/general/_hacks.scss

@@ -8,14 +8,14 @@ $default-has-layout-approach: zoom !default;
 // This mixin causes an element matching the selector
 // to gain the "hasLayout" property in internet explorer.
 // More information on [hasLayout](http://reference.sitepoint.com/css/haslayout).
-@mixin has-layout($using: $default-has-layout-approach) {
+@mixin has-layout($approach: $default-has-layout-approach) {
   @if $legacy-support-for-ie {
     @if $using == zoom {
       @include has-layout-zoom;
-    } @else if $using == block {
+    } @else if $approach == block {
       @include has-layout-block;
     } @else {
-      @warn "Unknown has-layout approach: #{$using}";
+      @warn "Unknown has-layout approach: #{$approach}";
       @include has-layout-zoom;
     }
   }