The PowerPC CPU has bits in MSR (DR and IR) which control whether
addresses are translated. We should respect these instead of mixing
physical addresses and translated addresses into the same address space.

This is mostly mass-renaming calls to memory accesses APIs from places
which expect address translation to use a different version from those
which do not expect address translation.

This does very little on its own, but it's the first step to a correct BAT
implementation.

This code originally tried to map the "low space" for the Gamecube's
memory layout, but since has expanded to mapping all of the easily
mappable memory on the system. Change the name to "GrabSHMSegment" to
indicate that we're looking for a shared memory segment we can map into
our process space.

These are effectively unused, since the memmap already maps them in one
place. For 32-bit, they might have some slight advantage, but we already
special-case the regular "high-mem" pointer for 32-bit, so just use the
one we already have...