Returns the virtual address (SPTR) of a process's process information block extension (PIBX).
pibx (pin)
pibx:sptr (pin:u16)
The process identification number (PIN) for which the address of the PIBX is to be returned.
$nmdebug > wl pibx(8) $c4680000
If the PIN does not exist, the function result is undefined and an error status is set.
