Break large portions of x86-specific code into a file separate from
xen_intr.c. A fair amount of the event channel code can be shared
among architectures, but the current lowest layer cannot.
The original implementation was done by Julien Grall in 2015, but this
has required very substantial updating.
Removal of PVHv1 meant substantial portions disappeared. The original
implementation took care of moving interrupt allocation to
xen_arch_int.c, but this has required massive rework and was broken off.
Submitted by: Elliott Mitchell <email@example.com>
Original implementation: Julien Grall <firstname.lastname@example.org>, 2015-10-20 09:14:56