libsa: Remove redundant sys/cdefs.h

Sponsored by: Netflix

stand: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

stand: use snprintf here

This code was written prior to snprintf being in the then libstand (now
libsa). Since we have it, use it for extra safety. The code already
tries to be safe, but since we have snprintf as well, the added layer of
protection will suffice. The current code reserves 16 bytes (plus a NUL)
at the end for worst case of inet_ntoa, which is still a little
pessimal, but safe from overflow.

Sponsored by: Netflix
Reviewed by: tsoome
Differential Revision: https://reviews.freebsd.org/D35102

libsa: bootp is using pointers with different sign

Just change bp_file to char and same for variable s.

Prefer uintXX_t to u_intXX_t

A foolish consistency is the hobgoblin of little minds, adored by
little statesmen and philosophers and divines. With consistency a
great soul has simply nothing to do. -- Ralph Waldo Emerson

libsa: Consolidate tftp sendrecv into net.c sendrecv

bootp/arp/rarp/rpc all use the sendrecv implementation in net.c. tftp has
its own implementation because it passes an extra parameter into the recv
callback for the received payload type to be held.

These sendrecv implementations are otherwise equivalent, so consolidate
them. The other users of sendrecv won't be using the extra argument to recv,
but this gives us only one place to worry about respecting timeouts and one
consistent timeout behavior.

Tested by: sbruno
Reviewed by: sbruno, tsoome
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D14373

dhcp_try_rfc1048() is not used any more

Remove unused function.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D13382

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix