libc: add adjtime() system call.

Implement the adjtime() system call and add a test for it to test69.
Additionally, install the adjtime.2 and clock_*.2 man pages.
inet: silence message about exceptions

	. inet: silence message about exceptions not being implemented
	  for select(UDP)

This message generates a lot of noise with openntpd. Hide it unless DEBUG is
turned on.

Change-Id: I1527a9ca2583601d6087456062b4f675c80dd711
Remove obsolete warning in sys/sys/sysctl header

Change-Id: Idb9b10922d00d4b3886c8247f352cc4ec5fe17b4
top: a few fixes

	. fixed overflow in ticks compare function, causing
	  occasionally esp. the kernel to be mis-ordered by cpu
	  time
	. fixed some const string related warnings
	. fixed some variable name shadowing warnings

Change-Id: I02c177b1579bce164372f9b03f6b472537cc9e3e
Importing usr.bin/ftp
etcfiles: Improve the "install" message
Importing usr.sbin/rdate

Import the NetBSD rdate command and remove the Minix rdate command.
The default behaviour for both is the same. The NetBSD version adds
options to just display the time, adjust the time using adjtime(),
and set the time without printing the time.

Porting Notes:
 - Compiles cleanly out of the box without any warnings
 - Path changes from /usr/bin/rdate to /usr/sbin/rdate
 - checked pkgsrc for any usages of rdate (none found)
 - checked src for any usages of rdate (none found)

Testing:
 - all command line options work (tested with time.nist.gov server)
 - Native and cross build OK

Change-Id: I613449763891a896527f337999c006a970c3924c
tests/run: add test69 to setuids.

test69 requires superuser powers to adjust the time. This caused
the test to fail when run as a normal user. The patch adds test69
to the setuid list which will allow regular users to execute it.

Patch contributed by Antoine Leca.
Adding missing dependency on libraries for hdboot

 * Also cleanup a bit the makefile.
 * Also removing small inconsistency for arm builds where log would be
   skipped if doing a make hdboot, but not when cross-compiling.

Change-Id: Ic9e20655234a667ea8a967d05589d4df46c2d521
Removing include/minix/limits.h

This files defines two constants which are only used through
sys/syslimits. So they where moved there instead of including the file
and it was removed.

Change-Id: Iba3d220144dddf5d6411a6c66e2f223a1aafb50f
Downgrading to netbsd zlib version

Change-Id: I83cf73d8357ea34ab5e49fe15bd4c45ce54cac01