void * GB.Hook ( int type , void * hook )
Installs a global interpreter hook.
There are six global hooks :
GB_HOOK_MAIN to parse the command line.
GB_HOOK_LOOP to manage the event loop.
GB_HOOK_WAIT to implement the WAIT instruction.
GB_HOOK_BEEP to implement the not yet existing BEEP instruction :-).
GB_HOOK_WATCH to watch a file descriptor.
GB_HOOK_POST to execute callback functions at the next call of the event loop.
This function returns the previous hook, so that you can call it yourself if
necessary. I think this is useful only to the GB_HOOK_MAIN hook.