Process core notes for a 32-bit process running on a 64-bit host need to
use 32-bit structures so that the note layout matches the layout of notes
of a core dump of a 32-bit process under a 32-bit kernel.
TODO: This is just the kernel part, I still need to fix gcore, and for
gcore since I need to export ptrace_lwpinfo32 to userland I'm going to
need to move various structures out of compat32-specific headers and
into sys/foo.h headers.