[wasm] Remove special memory type for (internal) globals and use local type instead.

src/wasm/ast-decoder.h

Index: src/wasm/ast-decoder.h
diff --git a/src/wasm/ast-decoder.h b/src/wasm/ast-decoder.h
index a0e98f7587ab227b3f4e7ffae8f3106024a1f9f9..527bb2e4780ba84bc1bafc547e6ed10431c9abf5 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -79,13 +79,11 @@ struct ImmF64Operand {
 struct GlobalIndexOperand {
   uint32_t index;
   LocalType type;
-  MachineType machine_type;
   unsigned length;
 
   inline GlobalIndexOperand(Decoder* decoder, const byte* pc) {
     index = decoder->checked_read_u32v(pc, 1, &length, "global index");
     type = kAstStmt;
-    machine_type = MachineType::None();
   }
 };