PowerPC Paravirtualization Support.

This handler encapulates the functionality (primarily conditional feature defines) related to paravirtualization on the PowerPC.

Paravirtualization on the PowerPC makes the following assumptions:

RTEMS executes in user space
In user space there is no access to the MSR.
Interrupt enable/disable support using the MSR must be disabled and replaced with BSP provided methods which are adapted to the hosting environment.