MFC r308139,r308157,r308160,r316818,r318250,r318443:

MFC r308139,r308157,r308160,r316818,r318250,r318443:

r308139 (by bapt):

cron(8): add support for /etc/cron.d and /usr/local/etc/cron.d

For automation tools it is way easier to maintain files in directories rather
than modifying /etc/crontab.

The files in those directories are in the same format as /etc/crontab

Relnotes:	yes

r308157 (by bapt):

Fix typo in cron(8) date

r308160 (by bapt):

syslogd(8): add an 'include' keyword

All the '.conf' files not beginning with a '.' contained int he directory
following the keyword will be included.

This keyword can only be used in the first level configuration files.

Modify the default syslogd.conf to 'include' /etc/syslog.d and
/usr/local/etc/syslog.d

It simplify a lot handling of syslog from automation tools.

Relnotes:	yes

r316818:

Conditionally install /etc/pam.d/ftp* and /etc/pam.d/telnetd

/etc/pam.d/ftp* should be installed with MK_FTP != no and
/etc/pam.d/telnetd should be installed when MK_TELNET != no.

r318250:

Handle the logfiles in newsyslog and syslogd conditionally, based on
src.conf(5) knobs

This will allow consumers of FreeBSD to use the unmodified configuration
files out of the box more than previously.

Both newsyslog.conf and syslog.conf:
- /var/log/lpd-errs (MK_LPR != no)
- /var/log/ppp.log (MK_PPP != no)
- /var/log/xferlog (MK_FTP != no)

newsyslog.conf:
- /var/log/amd.log (MK_AMD != no)
- /var/log/pflog (MK_PF != no)
- /var/log/sendmail.st (MK_SENDMAIL != no)

r318443:

Conditionally handle the crontab entry for atrun(8)

The default crontab prior to this commit assumes atrun(8) is always
present, which isn't true if MK_AT == no. Move atrun(8) execution
from /etc/crontab to /etc/cron.d/at, and base /etc/cron.d/at's installation
on MK_AT. cron(8) will detect /etc/cron.d/at's presence when the configuration
is loaded and run atrun every 5 minutes like it would prior to this commit.

SHELL and PATH are duplicated between /etc/crontab and /etc/cron.d/at
because atrun(8) executes programs, which may rely on environment
set in the current default /etc/crontab.

Noted by:	bdrewery (in an internal review)
Relnotes:	yes (may need to add environmental modifications to
		     /etc/cron.d/at)

git-svn-id: svn://svn.freebsd.org/base/stable/10@320222 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f