Drv_Int does not detect double defined IRQ priorities

It is possible to define multiple IRQ sources with the same priority, without an error being thrown.

Effect:
Interrupts attached to an already used vector will cause system freeze on interrupt request

Background:
Although rcX HAL does check if an interrupt vector is already in use, the result of this check is not passed to the user application. Thus rcX Kernel startup is not stopped and interrupts might be enabled without having a valid interrupt service routine registerd in the system.