[wasm] Support undefined indirect table entries, behind a flag.

test/mjsunit/wasm/wasm-constants.js

Index: test/mjsunit/wasm/wasm-constants.js
diff --git a/test/mjsunit/wasm/wasm-constants.js b/test/mjsunit/wasm/wasm-constants.js
index 389383e90a1306cc000027e96f66302ea427e599..6f953e89c27afee3725d02fd56a6de9b206581cb 100644
--- a/test/mjsunit/wasm/wasm-constants.js
+++ b/test/mjsunit/wasm/wasm-constants.js
@@ -303,6 +303,7 @@ var kTrapRemByZero            = 4;
 var kTrapFloatUnrepresentable = 5;
 var kTrapFuncInvalid          = 6;
 var kTrapFuncSigMismatch      = 7;
+var kTrapDefaultFuncCall      = 8;
 
 var kTrapMsgs = [
   "unreachable",
@@ -312,7 +313,8 @@ var kTrapMsgs = [
   "remainder by zero",
   "integer result unrepresentable",
   "invalid function",
-  "function signature mismatch"
+  "function signature mismatch",
+  "default function call"
 ];
 
 function assertTraps(trap, code) {