[PATCH v12 0/2 hurd] Add irqhelp library and clean up ddekit

[Damien Zammit]

Hi,

This patchset adds a new library irqhelp for assisting the attachment
of irq handlers in userspace.

The previous problem was that calling a function with a local param
from inside the wrapped_server_loop was crashing netdde
due to a bogus stack offset. This is fixed by removing the nested function
altogether and removes execution from the stack in interrupt.c

The mach_msg_server thread now shuts down cleanly by setting the
irq->port to a dead name outside of the irq handler thread, thus
not requiring a new interrupt to be triggered to shut the thread down.

TESTED: by compiling netdde.static and trying ifdown/ifup a few times
and transferring a large file from the vm.

Thanks,
Damien