[libc] Update libc.

1. Add POSIX termios implementation;
2. Add POSIX signals implementation;
3. Add stdio for each libc.

components/libc/compilers/dlib/libc.c

@@ -0,0 +1,59 @@
+/*
+ * File     : libc.c
+ * Brief    : iar dlib initialization
+ *
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2006 - 2017, RT-Thread Development Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2017/10/15     bernard      the first version
+ */
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <rtthread.h>
+
+#include "libc.h"
+
+#ifdef RT_USING_PTHREADS
+#include <pthread.h>
+#endif
+
+int libc_system_init(void)
+{
+#if defined(RT_USING_DFS) & defined(RT_USING_DFS_DEVFS)
+    rt_device_t dev_console;
+
+    dev_console = rt_console_get_device();
+    if (dev_console)
+    {
+    #if defined(RT_USING_POSIX_STDIN)
+        libc_stdio_set_console(dev_console->parent.name, O_RDWR);
+    #else
+        libc_stdio_set_console(dev_console->parent.name, O_WRONLY);
+    #endif
+    }
+#endif
+
+#if defined RT_USING_PTHREADS && !defined RT_USING_COMPONENTS_INIT
+    pthread_system_init();
+#endif
+
+    return 0;
+}
+INIT_COMPONENT_EXPORT(libc_system_init);