Remove await* from babel-generator, add parsing error to babylon - (fixes T6688)

src/parser/expression.js

@@ -968,7 +968,10 @@ pp.parseAwait = function (node) {
   if (this.isLineTerminator()) {
     this.unexpected();
   }
-  node.all = this.eat(tt.star);
+  node.all = false;
+  if (this.match(tt.star)) {
+    this.raise(node.start, "await* has been removed from the async functions proposal. Use Promise.all() instead.")
+  }
   node.argument = this.parseMaybeUnary();
   return this.finishNode(node, "AwaitExpression");
 };

test/fixtures/experimental/await/illegal-await-star/actual.js

@@ -0,0 +1,3 @@
+async function bar() {
+  await* foo();
+}

test/fixtures/experimental/await/illegal-await-star/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["asyncFunctions"],
+  "throws": "await* has been removed from the async functions proposal. Use Promise.all() instead. (2:2)"
+}