Log Message:
Update to 0.9.17. Changes:
- Implement RFC 4122 UUIDv1 identifier generation, more resistant to
  duplicate than our previous implementation in case of clock skew, or
  multiple client with the same analyzerid sending alert in parallel.
- You can now provide NULL value to idmef_path_set() in order to
  destroy existing value within an IDMEF message.
- Unify memory handling of value retrieval through idmef_path_t. This
  allow the user to retrieve and keep any values, even through the
  associated IDMEF message is freed.
- Build system cleanup, enable RELRO when possible.
- Implement PRELUDE_CLIENT_FLAGS_AUTOCONFIG, which is set by default,
  but that applications might unset in order for their client not to
  read the default profile/global configuration.
- Fix possible assertion when destroying un-started prelude-client.
- Improvement to the prelude-io API, the user might now hook its own
  handling function.
- Fix dumping of (not) NULL criteria operator to string. Remove
  gratuitous space insertion when dumping criteria.
- Headers fixes for C++ build.
- Fix printing and cloning of empty IDMEF string.
- In IDMEF to string convertion code, print <invalid enum value> in
  place of NULL on invalid enumeration value.
- Various bug fixes.