remove db2 backend from build tree
this fixes an accidental commit, but leaves some parts in place. Specifically, our 'beenthere' checks
were accidentally refusing to re-ask anything if *either* ipv4 or ipv6 had asked them already. This is now
sorta fixed.
add pubsuffix.cc to .gitignore
add bind-dnssec.db to gitignore in nobackend soa-edit test dir
update polarssl to 1.3.9
park ed25519 directory in ext
disable sqlite3 foreign keys by default
Merge pull request #1969 from mind04/gitignore

add bind-dnssec.db to gitignore in nobackend soa-edit test dir
Merge pull request #1971 from mind04/ed25519

park ed25519 directory in ext
Merge pull request #1970 from mind04/polarssl

update polarssl to 1.3.9
Merge pull request #1973 from mind04/gitignore2

add pubsuffix.cc to .gitignore
Merge pull request #1974 from mind04/fkeys

disable sqlite3 foreign keys by default
Merge pull request #1975 from mind04/db2

remove db2 backend from build tree
module makefiles and .gitignore
Merge pull request #1976 from mind04/gitignore

module makefiles and .gitignore
Add info on where to get the source.

 * Also document the key-id used to sign releases (closes 1446).