Get rid of the different kinds of yield in the AST & full-codegen.

src/parsing/parser.h

Index: src/parsing/parser.h
diff --git a/src/parsing/parser.h b/src/parsing/parser.h
index d4fb62f02c041fce4d752fda56a4d979b564d622..33236d025c9448f666942b0fde28f07451e721fb 100644
--- a/src/parsing/parser.h
+++ b/src/parsing/parser.h
@@ -444,6 +444,8 @@ class ParserTraits {
   Expression* BuildUnaryExpression(Expression* expression, Token::Value op,
                                    int pos, AstNodeFactory* factory);
 
+  Expression* BuildIteratorResult(Expression* value, bool done);
+
   // Generate AST node that throws a ReferenceError with the given type.
   Expression* NewThrowReferenceError(MessageTemplate::Template message,
                                      int pos);