LMDB-based very high performance backend
Merge branch 'lmdb-back' of https://github.com/mzealey/pdns into mzealey-lmdb-back

Conflicts:
	.travis.yml
silence bunch of warning in lmbdbbackend
add missing ' to error message
cleanup gsql-master regression test scripts
remove duplicate code from gsql-master test scripts
fix axfr source for goracle-slave tests
add postgress-slave mode to regression tests
use pdnssec for tsig keys and metadata in tests
add tests new tests to travis.yml
fix feedEnt query
run nodnssec slave tests without the (backend)-dnssec option
Merge pull request #1363 from mind04/fix

cleanup regression test scripts
candidate 3.6 recursor release notes
missed a bit of rec 3.6 release notes
prevent duplicate logging of TCP overflows
implement minimum-ttl-override setting and rec_constrol set-minimum-ttl for dealing with DoS
t_id check was wrong for pdns-distributes-queries
document minimum-ttl-override, rec_control set-minimum-ttl, status of pdns-distributes-queries
move a common error behind log-common-errors filter