Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

tests: sort & fix includes, remove -include from CFLAGS of acct tests

- Sort the includes of pack.c, moving sys/*.h files near the top.
- Add a couple of missing #include lines, and remove the need for
custom -include options in the CFLAGS of the test Makefile.
- Remove the ad-hoc 'all' target, but keep its 'regress' bits for
testing.
- Convert the ad-hoc 'clean' target to proper CLEANFILES stuff,
so that the normal bsd.prog.mk machinery can clean up.
- Use `make -V .OBJDIR' to detect the place where 'pack' lives,
so that regress.t works both with and without 'make obj'.

Reviewed by: uqs
MFC after: 1 week

Also cleanup after the test run.

Make sure 'pack' is usable for 'prove -r'.

Test the integer-arithmetic float conversions encode_timeval and encode_long
in kern_acct.c.