Various additions and fixes.

src/lib9/ffork-Darwin.c

@@ -1,26 +1 @@
-#include <lib9.h>
-#include <pthread.h>
-
-extern int __isthreaded;
-int
-ffork(int flags, void(*fn)(void*), void *arg)
-{
-	void *p;
-	pthread_t tid;
-
-	if(flags != (RFMEM|RFNOWAIT)){
-		werrstr("ffork unsupported");
-		return -1;
-	}
-
-	if(pthread_create(&tid, NULL, (void*(*)(void*))fn, arg) < 0)
-		return -1;
-	return (int)tid;
-}
-
-int
-getfforkid(void)
-{
-	return (int)pthread_self();
-}
-
+#include "ffork-pthread.c"