Adapt everything in BT5 to new capnhook API

This includes:
- Renaming of functions (iohook_invoke_next)
- Slight interface changes (com_proxy_wrap, iohook_push_handler)
- De-duplicate stuff from utils (iobuf, hr)

src/main/sdvxhook2-cn/acio.c

@@ -51,7 +51,7 @@ HRESULT ac_io_port_dispatch_irp(struct irp *irp)
     log_assert(irp != NULL);
 
     if (!ac_io_emu_match_irp(&ac_io_emu, irp)) {
-        return irp_invoke_next(irp);
+        return iohook_invoke_next(irp);
     }
 
     for (;;) {

src/main/sdvxhook2-cn/dllmain.c

@@ -37,10 +37,6 @@
 #define SDVXHOOK2_CN_CMD_USAGE \
     "Usage: launcher.exe -K sdvxhook2.dll <soundvoltex.dll> [options...]"
 
-static const irp_handler_t sdvxhook_handlers[] = {
-    ac_io_port_dispatch_irp,
-};
-
 struct sdvxhook2_cn_config config_cn;
 struct camhook_config_cam config_cam;
 struct d3d9exhook_config_gfx config_gfx;
@@ -90,7 +86,8 @@ static bool my_dll_entry_init(char *sidcode, struct property_node *param)
 
     /* iohooks are okay, even if emu is diabled since the fake handlers won't be
      * used */
-    iohook_init(sdvxhook_handlers, lengthof(sdvxhook_handlers));
+    iohook_push_handler(ac_io_port_dispatch_irp);
+
     rs232_hook_init();
     rs232_hook_limit_hooks();