Group the integer computation in a pointer increment.
Change inflate_fast() to avoid pointer subtraction.

Fully avoiding pointer subtraction requires that POSTINC be defined.

This change is probably not quite upstreamable as is given that support
exits for assember version of inflate_fast.
Address another case of pointer subtraction.
Modify the updatewindow function to take the beginning rather than the
end of the data to be copied.
Remove another case of pointer subtraction.
Fix the signature of memchar_c_const.
Include the trailing c in crc32_c
Use a cast rather than cheri_getbase to free something when we might be
in a sandbox.