PowerPC 601 need specific callbacks for its BATs setup.

PowerPC 601 need specific callbacks for its BATs setup.
Implement PowerPC 601 HID0 register, needed for little-endian mode support.
As a consequence, we need to merge hflags coming from MSR with other ones.
Use little-endian mode from hflags instead of MSR during code translation.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3524 c046a42c-6fe2-441c-8c8c-71466251a162