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/set-host.c

@@ -24,7 +24,7 @@ ssize_t
 _hurd_set_host_config (const char *item, const char *value, size_t valuelen)
 {
   error_t err;
-  mach_msg_type_number_t nwrote;
+  vm_size_t nwrote;
   file_t new, dir;
   char *name;