IopCreateObjectTypes: Add a DeleteProcedure for Device Objects.

IopCreateObjectTypes: Add a DeleteProcedure for Device Objects.
IopUnloadDevice: After calling the drivers Unload routine, make the DriverObject temporary and dereference it.
IopUnloadDriver: Check that the driver is not already unloading before trying to call unload routine.
If any failure, dereference the DriverObject before returning STATUS code.
On an attempt to unload the driver, loop through each DeviceObject and set DOE_UNLOAD_PENDING in device extensions flags.
Before calling the driver's unload routine set DRVO_UNLOAD_INVOKED in DriverObject's flags.
Fixes Bugchecks when attempting to load driver a second time and when unloading a driver that has upper level device attached.

svn path=/trunk/; revision=41254