[RFC] make VM handling async

Yeah, I know I'm on vacation, but without coding I die of boringness in less than a week.

This patchset is currently based on Jeromes VA fencing patch, but in the end makes it superfluous. It just moves the whole VM handling into the CP ring, removing the need to wait for anything directly in the VM code, the any waiting that happens is now in the allocation of page tables and that happens only on allocation of new VM space and not on freeing it, which in turn makes handling allot more simpler.

It's not 100% complete cause page table updates should be made with the DMA ring, but we haven't released documentation for that yet, so I currently use CP memory writes instead.

Please take a look and tell me what you think about it.

Cheers, Christian.