[HAL]

Implement lazy irql for APIC. This is useful for VMs, since APIC usually has high overhead due to the need of invoking the hypervisor on every irql raise and lower. With lazy irql we avoid that until absolutely neccessary. Note that we misuse the PCR's IRR field to save the current hardware irql. Its a huge performance boost (some parts take half the time), making APIC performance close to PIC performance on VBox. This is something that Windows doesn't have :)

svn path=/trunk/; revision=53695