Direct commit to stable

Remove libstand32 here. pc98 is a 32-bit platform, so it shouldn't compile
the extra 32-bit copy of libsa. The copy built in libstand is already 32-bit.
Add a comment saying we need an empty Makefile.pc98 since otherwise it would
pull in Makefile.i386 and there is no EFI on pc98, and the machines are too
old to have ZFS or GELI be a viable option (and besides, those don't compile).

Note: We also need r331140 to be MFC'd for pc98 build to work in all cases.