[es6] emit error when for-in loop declarations are initialized in strict mode

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index d93faaf0e1d8cfc8434b35f891eec1aeed16f2b6..b0c3ffe9cf38aa52e8b5c69eb3a2856a16a6564f 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -912,6 +912,7 @@ class Parser : public ParserBase<ParserTraits> {
                                    VariableDeclarationProperties* decl_props,
                                    ZoneList<const AstRawString*>* names,
                                    const AstRawString** out,
+                                   Scanner::Location* first_initializer_loc,
                                    bool* ok);
   Statement* ParseExpressionOrLabelledStatement(
       ZoneList<const AstRawString*>* labels, bool* ok);