* pluto: Obsoleted force_keepalive= and --force_keepalive

It violates RFC 3947/3948 where an explicit DOS is mentioned. It was
not enabled per default. It would not actually accomplish keeping the
NAT mapping open in the opposite direction.
* updated changes
prettypolicy: Avoid buffer length computations

This ensures that snprintf is not called with a length argument of
zero.
readwhackmsg: Guard against integer overflow when rounding up length
alg_enum_search_prefix, alg_enum_search_ppfix: Guard against long prefix

Existing callers use short, constant strings, so this does not make a
difference at present.
spawn_worker: Call _exit instead of exit in the child process

This suppresses unwanted cleanup actions.
Remove random_devices variable from programs/pluto/rnd.c
linux/net/ipsec/prng.c: Remove, no longer used
get_rnd_bytes: Abort on random number generator failure

We must not return without overwriting the buffer.
db_trans_expand, db_attrs_expand: Use ptrdiff_t for the pointer offset

This still invokes undefined behavior, but is more 64 bit safe.