sql/ticker: experimental multi-database ticker written in C

sql/ticker: experimental multi-database ticker written in C

The new ticker is based on libevent, uses single-threaded
async  architecture.

It can handle all databases in one Postgres instance, so you
need only one ticker instance per Postgres instance.

By default it autodetects all accessible databases and
whether they have PGQ installed.

Missing features ATM:
- logging
- config files
- daemonizing
- error handling

So it's not production quality yet..