hurd: Fix vm_size_t incoherencies

In gnumach, 3e1702a65fb3 ("add rpc_versions for vm types") changed the type
of vm_size_t, making it always a unsigned long. This made it incompatible on
x86 with size_t. Even if we may want to revert it to unsigned int, it's
better to fix the types of parameters according to the .defs files.

hurd/fd-write.c

@@ -26,7 +26,7 @@ _hurd_fd_write (struct hurd_fd *fd,
 		const void *buf, size_t *nbytes, loff_t offset)
 {
   error_t err;
-  mach_msg_type_number_t wrote;
+  vm_size_t wrote;
 
   error_t writefd (io_t port)
     {