pthread: Implement pthread_gettid_np
which is provided by bionic libc:
@@ -526,6 +526,7 @@ void pthread_yield(void);
/* A thread may obtain a copy of its own thread handle. */
#define pthread_self() ((pthread_t)gettid())
+#define pthread_gettid_np(thread) ((pid_t)(thread))
/* Compare two thread IDs. */
