[POWERPC] memory cleanup (phase 2), destroy (et. al) now work

[POWERPC] memory cleanup (phase 2), destroy (et. al) now work

The patch fixes the following problems:
  - Fix initializing the heaps so we can Link anywhere < RMA.  We not
    link xen at 4MiB, which is way saner.
  - We track and allocate pages (especially RMA) based on order.
  - free domain memory as a resource not as domain
  - clarify "order" arithmetic
  - update stale def of fix IS_XEN_HEAP_FRAME()

Signed-off-by: Jimi Xenidis <jimix@watson.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>