CorePlugin: signal to hook mapping updates of PCI descriptors

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
pci.c: notifying S2E of updates to PCI mappings

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
SymbolicHardware: cosmetic fixes

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
SymbolicHardware: fixed registering of symbolic I/O ranges for PCI devices

Can't use post_load hook as the PCI device might be unmapped at that time.

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>
docs: updated device driver tutorial

Signed-off-by: Vitaly Chipounov <vitaly.chipounov@epfl.ch>