Turn assert functionality standard-conforming in jerry-libc

Introducing the `assert.h` public header with the `assert(x)` macro
and already making use of it in jerry-libc sources. These newly
introduced ISO C-conforming features replace the non-conforming
`LIBC_ASSERT` and `LIBC_NDEBUG` at no cost, and they also have the
benefit that we can expose `assert` in a public header and make it
useful to jerry-libc users.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-libc/include/assert.h

@@ -0,0 +1,45 @@
+/* Copyright 2016 Samsung Electronics Co., Ltd.
+ * Copyright 2016 University of Szeged.
+ *
+ * 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.
+ */
+
+#ifndef JERRY_LIBC_ASSERT_H
+#define JERRY_LIBC_ASSERT_H
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif /* !__cplusplus */
+
+#ifndef NDEBUG
+#define assert(x) \
+  do \
+  { \
+    if (__builtin_expect (!(x), 0)) \
+    { \
+      fprintf (stderr, "%s:%d: %s: Assertion `%s' failed.", __FILE__, __LINE__, __func__, #x); \
+      abort (); \
+    } \
+  } while (0)
+#else
+#define assert(x) ((void) 0)
+#endif /* !NDEBUG */
+
+#ifdef __cplusplus
+}
+#endif /* !__cplusplus */
+#endif /* !JERRY_LIBC_ASSERT_H */