Refactor database initialisation in feedlog.pl.

Refactor database initialisation in feedlog.pl.

* Move database initialisation to a separate function.

* (Re-)try to connect every five seconds
  (instead of going into an endless loop) and
  log successful (re-)connections.

* Log postings that are dropped due to database failures
  to syslog (Message-ID) for recovery.

* If the connection to the database is lost, try to
  recover it (every five seconds) and try again to
  write the pending data.

* Input will be buffered automatically by INN until
  feedlog is able to process it (see man 5 newsfeeds).

Fixes #30, #31.

Signed-off-by: Thomas Hochstein <thh@inter.net>