This patch replaces the error-prone manual locking with the use of the
'Synced_interface' for the motherboard and the VCPU dispatcher. It also
removes all globally visible locks. Locks are now explicitly passed to
subsystems when needed.
Vancouver can now assign block devices to guests using the Block
interface. The machine has to be configured to use a specified drive,
which could be theoretically routed to different partitions or services
via policy definitions. Currently the USB driver only supports one
device. Genode's AHCI driver is untested.
If the session quota is too low, random pagefaults can occur on the
stack.
According to @Nils-TUD, it is necessary to protect the DiskCommit
messages with a lock against deadlocking with the timer. Observations
showed that this mitigates some problems with Gentoo on real hardware.
