machine: when invoking x86emu interrupts, switch to the kernel address space (which should already have the first 1 MB available) - entering the debugger with a VBE mode doesn't try and allocate physical memory any longer.
utilities: if we aren't locking, use the unlocked version of PhysicalMemoryManager::freePage (as we will already hold the pmem lock)
x86: no need to release the pmem lock before compacting caches any longer. Also implemented freePage as a call to freePageUnlocked to remove the duplicated code.