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/bsthook/dllmain.c

@@ -20,10 +20,6 @@
 #include "util/defs.h"
 #include "util/log.h"
 
-static const irp_handler_t bsthook_handlers[] = {
-    ac_io_bus_dispatch_irp,
-};
-
 static bool my_dll_entry_init(char *sidcode, struct property_node *config);
 static bool my_dll_entry_main(void);
 
@@ -116,7 +112,7 @@ BOOL WINAPI DllMain(HMODULE self, DWORD reason, void *ctx)
     args_free(argc, argv);
 
     app_hook_init(my_dll_entry_init, my_dll_entry_main);
-    iohook_init(bsthook_handlers, lengthof(bsthook_handlers));
+    iohook_push_handler(ac_io_bus_dispatch_irp);
     rs232_hook_init();
 
     gfx_init();