. strerror() assumes this
. remove generated libminc/errlist.c
. errno's in <sys/errno.h> have to be in sorted order
. filtering out some errno.h in Makefile lets us use near-stock
errlist.awk
Now users can choose between libsys, libsys + libminc and
libsys + libc. E.g. PUFFS/FUSE servers need libsys + libc while
old servers can use libsys + libminc.