control: Refactored control socket for registerable commands.
contol: move the control register command into the header file

Signed-off-by: Juhász Viktor <jviktor@balabit.hu>
control: rename the Commands to ControlCommand and some minor renaming are also made

Signed-off-by: Juhász Viktor <viktor.juhasz@balabit.com>
afsql: Fixed memleak in `afsql_dd_insert_db()`.

When a transaction failed we just returned and leaked all
the allocated resources.

Signed-off-by: Budai Laszlo <Laszlo.Budai@balabit.com>
Merge pull request #351 from lbudai/f/fixes-from-3.6

F/fixes from 3.6
Preparations for syslog-ng 3.7.0alpha2

Bumped the version in VERSION, and added changes to NEWS.md.

Signed-off-by: Budai Laszlo <Laszlo.Budai@balabit.com>