support posix

1. posix pthread.h: pthread, pthread_barrier, pthread_cond, pthread_mutex, , pthread_rwlock, pthread_spin, etc
2. posix semaphore.h: sem_*
3. posix mqueue.h: mq_*
4. posix time.h: timer_*
5. to support posix, add tos_barrier, tos_bitmap, tos_rwlock, tos_stopwatch, change name of k_task_t from a char * pointer to a char array.
6. sample, see examples\posix
7. project, see board\TencentOS_tiny_EVB_MX_Plus\KEIL\posix

osal/posix/include/signal.h

@@ -0,0 +1,37 @@
+/*----------------------------------------------------------------------------
+ * Tencent is pleased to support the open source community by making TencentOS
+ * available.
+ *
+ * Copyright (C) 2019 THL A29 Limited, a Tencent company. All rights reserved.
+ * If you have downloaded a copy of the TencentOS binary from Tencent, please
+ * note that the TencentOS binary is licensed under the BSD 3-Clause License.
+ *
+ * If you have downloaded a copy of the TencentOS source code from Tencent,
+ * please note that TencentOS source code is licensed under the BSD 3-Clause
+ * License, except for the third-party components listed below which are
+ * subject to different license terms. Your integration of TencentOS into your
+ * own projects may require compliance with the BSD 3-Clause License, as well
+ * as the other licenses applicable to the third-party components included
+ * within TencentOS.
+ *---------------------------------------------------------------------------*/
+
+#ifndef _POSIX_SIGNAL_H_
+#define  _POSIX_SIGNAL_H_
+
+#include "sys/types.h"
+
+union sigval {
+    int     sival_int;  /* integer signal value */
+    void   *sival_ptr;  /* pointer signal value */
+};
+
+struct sigevent {
+    int             sigev_notify;   /* notification type */
+    int             sigev_signo;    /* signal number */
+    union sigval    sigev_value;    /* signal value */
+    void            (*sigev_notify_function)(union sigval);      /* notification function */
+    pthread_attr_t  *sigev_notify_attributes;   /* notification attributes */
+};
+
+#endif /* _POSIX_SIGNAL_H_ */
+