simplify cancellation push/pop slightly

no need to pass unnecessary extra arguments on to the core code in
pthread_create.c. this just wastes cycles and code bloat.

src/thread/cancellation.c

 #include "pthread_impl.h"
 
-void __do_cleanup_push();
-void __do_cleanup_pop();
+static void dummy(struct __ptcb *cb)
+{
+}
+weak_alias(dummy, __do_cleanup_push);
+weak_alias(dummy, __do_cleanup_pop);
 
 void _pthread_cleanup_push(struct __ptcb *cb, void (*f)(void *), void *x)
 {
 	cb->__f = f;
 	cb->__x = x;
-	__do_cleanup_push(cb, f, x);
+	__do_cleanup_push(cb);
 }
 
 void _pthread_cleanup_pop(struct __ptcb *cb, int run)
 {
-	__do_cleanup_pop(cb, run);
+	__do_cleanup_pop(cb);
 	if (run) cb->__f(cb->__x);
 }
-
-static void dummy()
-{
-}
-weak_alias(dummy, __do_cleanup_push);
-weak_alias(dummy, __do_cleanup_pop);

src/thread/pthread_create.c

@@ -43,14 +43,14 @@ void pthread_exit(void *result)
 	__syscall(SYS_exit, 0);
 }
 
-void __do_cleanup_push(struct __ptcb *cb, void (*f)(void *), void *x)
+void __do_cleanup_push(struct __ptcb *cb)
 {
 	struct pthread *self = pthread_self();
 	cb->__next = self->cancelbuf;
 	self->cancelbuf = cb;
 }
 
-void __do_cleanup_pop(struct __ptcb *cb, int run)
+void __do_cleanup_pop(struct __ptcb *cb)
 {
 	__pthread_self()->cancelbuf = cb->__next;
 }