call exit rather than _exits inside exits,

so that the c library atexit handlers get
a chance to run.

src/lib9/atexit.c

@@ -50,5 +50,5 @@ exits(char *s)
 			onex[i].f = 0;
 			(*f)();
 		}
-	_exits(s);
+	exit(s && *s ? 1 : 0);
 }

src/lib9/exits.c

@@ -1,22 +0,0 @@
-#include <u.h>
-#include <libc.h>
-
-extern void _privdie(void);
-
-void
-exits(char *s)
-{
-	_privdie();
-	if(s && *s)
-		exit(1);
-	exit(0);
-}
-
-void
-_exits(char *s)
-{
-	_privdie();
-	if(s && *s)
-		_exit(1);
-	_exit(0);
-}