Merge branch 'sql' into 'master'

README.md

backend/backend.go

backend/ldap/ldap.go

backend/sql/sql.go

dovecot/keyproxy.go

server/keystore.go

server/keystore_test.go

vendor/github.com/go-sql-driver/mysql/AUTHORS

vendor/github.com/go-sql-driver/mysql/CHANGELOG.md

vendor/github.com/go-sql-driver/mysql/CONTRIBUTING.md

vendor/github.com/go-sql-driver/mysql/LICENSE

vendor/github.com/go-sql-driver/mysql/README.md

vendor/github.com/go-sql-driver/mysql/appengine.go

vendor/github.com/go-sql-driver/mysql/auth.go

vendor/github.com/go-sql-driver/mysql/buffer.go

vendor/github.com/go-sql-driver/mysql/collations.go

vendor/github.com/go-sql-driver/mysql/conncheck.go

vendor/github.com/go-sql-driver/mysql/conncheck_windows.go

vendor/github.com/go-sql-driver/mysql/connection.go

vendor/github.com/go-sql-driver/mysql/const.go