x86 platforms that use an IOAPIC route the legacy timer interrupt (IRQ0) to
pin 2 of the IOAPIC.

Add an 'Interrupt Source Override' entry to the MADT to describe this
and start asserting interrupts on pin 2 in the 8254 device model.

Submitted by:	Tycho Nightingale (tycho.nightingale@pluribusnetworks.com)
Update svn from 1.8.1 to 1.8.4 - minor security fixes and client side
merge handling bug fixes (reintegrate, mergeinfo etc)