Make locks more reliable

This change switches most of the core locks to be re-entrant, in order
to reduce the chance of deadlocking code that does, clever things with
asynchronous signal handlers. This change implements it it in pthreads
so we're one step closer to having a standardized threading primitives

libc/log/vflogf.c

@@ -78,6 +78,9 @@ static void vflogf_onfail(FILE *f) {
  *
  * In that case, the second log entry will always display the amount of
  * time that it took to connect. This is great in forking applications.
+ *
+ * @asyncsignalsafe
+ * @threadsafe
  */
 void(vflogf)(unsigned level, const char *file, int line, FILE *f,
              const char *fmt, va_list va) {