Support strict mode detection in the pre-scanner. (#3450)

Furthermode an error is thrown when 'use strict' is used in a function with non-simple arguments
and function arguments are not moved to lexical environment when unmapped arguments are present.

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

tests/jerry/es2015/directive.js

@@ -0,0 +1,35 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// 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.
+
+function check_syntax_error (code)
+{
+  try {
+    eval (code)
+    assert (false)
+  } catch (e) {
+    assert (e instanceof SyntaxError)
+  }
+}
+
+eval("function f(a, b = 4) { }")
+check_syntax_error ("function f(a, b = 4) { 'use strict' }")
+
+eval('function f(...a) { }')
+check_syntax_error ('function f(...a) { "use strict" }')
+
+eval("({ f([a,b]) { } })")
+check_syntax_error ("({ f([a,b]) { 'use strict' } })")
+
+eval("function f(a, b = 4) { 'directive1'\n'directive2'\n }")
+check_syntax_error ("function f(a, b = 4) { 'directive1'\n'directive2'\n'use strict' }")