init script: support DAEMON_ARGS

Support additional command line parameters by sourcing
/etc/default/pdns and taking DAEMON_ARGS from there.
init script: ensure socket dir exists

This is an old change in Debian that is apparently necessary on some
(newer) systems where the socket dir might vanish on reboot.
Merge pull request #1724 from zeha/f/fix-1149

pdns init script improvements, fixes #1149, closes #1721 (thanks @tuxis-ie as well!)
document 3.4.0-rc2; move rec 3.6.1 behind it
clarify, thanks @mind04
send empty SERVFAIL after a backend throws a DBException
DNAME don't sign the synthesised CNAME
update download url in release notes
Merge pull request #1725 from mind04/servfail

send empty SERVFAIL after a backend throws a DBException
Merge pull request #1726 from mind04/dname

DNAME don't sign the synthesised CNAME
make sure that if we can't reload our configuration file on reload-acls, we don't revert our acls
to the built-in defaults, but retain the old configuration. Closes #1728. Thanks to Andreas Jakum for spotting this issue.
update canary
correct error message
Update pdns_with_postgresql.m4

Small patch to fix compilation on FreeBSD (and possibly other UNIX distributions)
Merge pull request #1733 from mind04/doc

update el download url in release notes
Merge pull request #1731 from RvdE/patch-3

Update pdns_with_postgresql.m4
raise log level on dlerror(), fixes #1734, thanks @James-TR
use kernel recorded arrival time for question/answer latency measurements, so we include the queue of packets waiting for userland attention in our stats. could be bad.
Update Makefile.am

Install man1/disdist.1 when building tools
Make sure yahttp is linked into remotebackend

Make sure that the yahttp directory is built first
and then link in the resulting library.

Checked with readelf -s .libs/libremotebackend.so | grep NOTYPE
that this fixes the undefined symbol.

Fixes #1732