Make less.js ignore nodes in its own path so infinite recursion does not happen. Fixes #413

test/css/mixins.css

@@ -106,3 +106,6 @@ h3 + * {
   background-image: "/a.png";
   background-position: center center;
 }
+.recursion {
+  color: black;
+}

test/less/mixins.less

@@ -91,3 +91,9 @@ h3 { .margin_between(15px, 5px); }
   @s: "/";
   .mixin_def( "@{s}a.png", center center);
 }
+.recursion() {
+  color: black;
+}
+.recursion {
+  .recursion();
+}