Change RTC time drift IRQ re-injection (Gleb Natapov)

Change RTC time drift IRQ re-injection (Gleb Natapov)

Currently IRQ are reinjected as soon as they are acknowledged to
the RTC, but Windows sometimes do acknowledgement in a loop with
global interrupt disabled waiting for interrupt to be cleared and
it does not mask RTC vector in PIC/APIC while doing this. In such
situation interrupt injection always fails and RTC interrupt is never
cleared.

Instead of reinjecting coalesced IRQs on acknowledgement the patch below
reinjects them by accelerating RTC clock a bit. This way RTC interrupt
is not constantly raced after coalesced interrupt.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7231 c046a42c-6fe2-441c-8c8c-71466251a162