Implement WinNT condition variables, add semaphors

include/bh/internal/thread_posix.h

@@ -1,4 +1,5 @@
 #include <pthread.h>
+#include <semaphore.h>
 
 struct bh_thread_s
 {
@@ -11,6 +12,11 @@ struct bh_mutex_s
     pthread_mutex_t handle;
 };
 
+struct bh_semaphore_s
+{
+    sem_t handle;
+};
+
 struct bh_cond_s
 {
     pthread_cond_t handle;
@@ -22,6 +28,10 @@ int bh_thread_init(bh_thread_t *thread,
 int bh_mutex_init(bh_mutex_t *mutex);
 void bh_mutex_destroy(bh_mutex_t *mutex);
 
+int bh_semaphore_init(bh_semaphore_t *semaphore,
+                      int count);
+void bh_semaphore_destroy(bh_semaphore_t *semaphore);
+
 int bh_cond_init(bh_cond_t *cond);
 void bh_cond_destroy(bh_cond_t *cond);