Extension description syntax; extension instantiation, field values and calls with arguments (except strings); example of a simple extension.

String arguments support is supposed to be added in a subsequent commit.

tests/jerry/extensions.js

@@ -0,0 +1,32 @@
+// Copyright 2015 Samsung Electronics Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// TODO: Test other field types
+// TODO: Test functions
+
+assert(Jerry.io.platform === "linux");
+
+Jerry.io.print_uint32 (1);
+
+try
+{
+  // Argument type mismatch
+  Jerry.io.print_uint32 ('1');
+
+  assert (false);
+}
+catch (e)
+{
+  assert (e instanceof TypeError);
+}