Core: fixed ioctl(FIOASYNC) argument type

The documented argument type for this operation is an integer boolean.
Passing 1 as u_long makes the call silently fail on 64-bit big-endian
platforms, as the kernel receives only high 4 bytes set to 0.

src/os/unix/ngx_process.c

@@ -87,7 +87,7 @@ ngx_pid_t
 ngx_spawn_process(ngx_cycle_t *cycle, ngx_spawn_proc_pt proc, void *data,
     char *name, ngx_int_t respawn)
 {
-    u_long     on;
+    int        on;
     ngx_pid_t  pid;
     ngx_int_t  s;