[wasm] Add utilities to print out WASM ast directly from the bytes.

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 5b95ad9f870a93bbab3e54142a04dc9fe35bbafc..67aae6096d54c8d283210c4529f3355811e4f177 100644
--- a/src/wasm/ast-decoder.h
+++ b/src/wasm/ast-decoder.h
@@ -89,6 +89,8 @@ TreeResult VerifyWasmCode(FunctionEnv* env, const byte* base, const byte* start,
 TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env, const byte* base,
                         const byte* start, const byte* end);
 
+void PrintAst(FunctionEnv* env, const byte* start, const byte* end);
+
 inline TreeResult VerifyWasmCode(FunctionEnv* env, const byte* start,
                                  const byte* end) {
   return VerifyWasmCode(env, nullptr, start, end);