wast: Temporarily add back struct.new

I accidentally removed the old 'struct.new' instruction when updating the GC
proposal implementation too early, as SpiderMonkey still relies on it. The
struct.narrow instruction is in the same situation.

crates/wast/src/ast/expr.rs

@@ -521,6 +521,9 @@ instructions! {
         // gc proposal: eqref
         RefEq : [0xd5] : "ref.eq",
 
+        // gc proposal (moz specific, will be removed)
+        StructNew(ast::Index<'a>) : [0xfb, 0x0] : "struct.new",
+
         // gc proposal: struct
         StructNewWithRtt(ast::Index<'a>) : [0xfb, 0x01] : "struct.new_with_rtt",
         StructNewDefaultWithRtt(ast::Index<'a>) : [0xfb, 0x02] : "struct.new_default_with_rtt",

crates/wast/src/resolve/names.rs

@@ -1943,7 +1943,8 @@ impl<'a, 'b> ExprResolver<'a, 'b> {
                 }
             }
 
-            StructNewWithRtt(i)
+            StructNew(i)
+            | StructNewWithRtt(i)
             | StructNewDefaultWithRtt(i)
             | ArrayNewWithRtt(i)
             | ArrayNewDefaultWithRtt(i)