fix regression in the transform api

frameworks/compass/stylesheets/compass/css3/_transform-v2.scss

@@ -110,7 +110,7 @@ $default-skew-y      : 5deg                  !default;
   $origin-x: $default-origin-x,
   $origin-y: $default-origin-y,
   $origin-z: false,
-  $only3d:   false
+  $only3d:   if($origin-z)
 ) {
   $origin: unquote('');
   @if $origin-x or $origin-y or $origin-z {

lib/compass/sass_extensions/functions/if.rb

@@ -1,7 +1,7 @@
 module Compass::SassExtensions::Functions::If
-  def if(truth, if_true, if_false = nil)
+  def if(truth, if_true = nil, if_false = nil)
     if truth.to_bool
-      if_true
+      if_true || Sass::Script::Bool.new(true)
     else
       if_false || Sass::Script::Bool.new(false)
     end