libsyntax: Pretty print using the new impl syntax. r=brson

src/libsyntax/print/pprust.rs

@@ -554,15 +554,17 @@ pub fn print_item(s: @ps, &&item: @ast::item) {
             print_type_params(s, tps);
             space(s.s);
         }
-        print_type(s, ty);
 
         match opt_trait {
             Some(t) => {
-                word_space(s, ~":");
                 print_path(s, t.path, false);
+                space(s.s);
+                word_space(s, ~"for");
             }
             None => ()
         };
+
+        print_type(s, ty);
         space(s.s);
 
         if methods.len() == 0 {

src/test/run-pass/class-attributes-1.rs

@@ -14,7 +14,7 @@ struct cat {
     name: ~str,
 }
 
-impl cat: Drop {
+impl Drop for cat {
     #[cat_dropper]
     fn finalize(&self) { error!("%s landed on hir feet" , self . name); }
 }

src/test/run-pass/method-attributes.rs

@@ -19,7 +19,7 @@ trait frobable {
 }
 
 #[int_frobable]
-impl int: frobable {
+impl frobable for int {
     #[frob_attr1]
     fn frob() {
         #[frob_attr2];