hw: avoid mandatory function calls in assertions

ref #528
hw: no implicit uint-to-int cast in signal submit

ref #528
hw: no mandatory asserts in platform thread

ref #528
hw: no asserts in platform PD

ref #528
hw: no assertions in pagers

ref #528
hw: avoid syscall fptr. array + threads can crash

ref #528
hw: kernel configuration in dedicated header

ref #528
hw: object in extra header & asserts reviewed

ref #528
hw: scheduler in extra header & asserts reviewed

ref #528
hw: IRQ receiver in extra header & reviewed

ref #528
hw: IPC node in extra header

ref #528
base: provide class Genode::Fifo_element

ref #528
hw: signal receiver in extra header without assert

ref #528
hw: add missing include in singleton header

ref #528
hw: PD in extra header with asserts reviewed

ref #528
hw: thread in extra header with asserts reviewed

ref #528
hw: no assert checks by default, enable opt-in

fix #528
hw: completely release signal-context resources

ref #589
base: destruct signal receiver platform specific

This is made for future signal framework in base-hw
wich needs a platform specific hook in the signal-
receiver destruction.

ref #589
hw: destruct signal receivers

ref #589