Memmap: Clean up indentation and whitespace a bit
MemArena: Remove duplicated code

I can't find any obvious difference between these two paths.
MemmapFunctions: Remove unused effective_address argument
Memmap: Make the constants aligned to 8 nibble characters

Otherwise, the constants can be a bit confusing to read.
MemArena: Bail on Arch64 if the out_ptr allocation fails
MemoryWindow: Use p_pFakeVMEM, not the virtual mirror

They point to the same contents, so there's no reason to use the
mirror. This lets us make all the mirrors static.
Memmap: Remove vestigals of the memory-mapped EFB

It hasn't been memory-mapped for a long time.
MemArena: Remove the low mappings for our pointers

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...
MemArena: Clean up the code that does the mirroring
MemArena: Rename GrabLowMemSpace to GrabSHMSegment

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.
Merge pull request #1425 from magcius/memmap-cleanup

Memmap: Cleanup code