Update rsyslog to 8.15.0
Switch to libfastjson, which will become a requirement in the next release.

- KSI Lib: Updated code to run with libksi 3.4.0.5
- KSI utilities: Added option to ser publication url.
- KSI Lib: Fixed wrong TLV container for KSI signatures from 0905 to 0906.
- KSI/GT Lib: Fixed multiple issues found using static analyzer
- performance improvement for configs with heavy use of JSON variables
- added pmpanngfw: contributed module for translating Palo Alto Networks
  logs.
- testbench: Changed valgrind option for imtcp-tls-basic-vg.sh
- pmciscoios: support for asterisk before timestamp added
- solr external output plugin much enhanced
- omrabbitmq: improvements
- add support for libfastjson (as a replacement for json-c)
- KSI utilities: somewhat improved error messages
- pmciscoios: support for some format variations
- support grok via new contributed module mmgrok
- omkafka: new statistics counter "maxoutqsize"
- improvments for 0mq modules:
  - omczmq: suspend / Retry handling - the output plugin can now recover
    from some error states due to issues with plugin startup or message
    sending
  - omczmq: refactored topic handling code for ZMQ_PUB output to be
    a little more efficient
  - omczmq: added ability to set a timeout for sends
  - omczmq: set topics can be in separate frame (default) or part
    of message frame (configurable)
  - omcmzq: code cleanup
  - imczmq: code cleanup
  - imczmq: fixed a couple of cases where vars could be used uninitialized
  - imczmq: ZMQ_ROUTER support
  - imczmq: Fix small memory leak from not freeing sockets  when done
    with them
  - allow creation of on demand ephemeral CurveZMQ certs for encryption.
- cleanup on code to unset a variable
- omelasticsearch: build on FreeBSD
- pmciscoios: fix some small issues clang static analyzer detected
- testbench: many improvements and some new tests
- overall code improvements thanks to clang static analyzer
- gnutls fix: Added possible fix for gnutls issue #575
- bugfix omkafka: restore ability to build on all platforms
- bugfix omkafka: fix potentially negative partition number
- bugfix: solve potential race in creation of additional action workers
- bugfix: potential memory leak in config parsing
- bugfix: small memory leak in loading template config
- bugfix: fix extra whitespace in property expansions
- bugfix: mmfields leaked memory if very large messages were processed
- bugfix: mmfields could add garbagge data to field
- bugfix: omhttpfs now also compiles with older json-c lib
- bugfix: memory leak in (contributed) module omhttpfs
- bugfix: parameter mismatch in error message for wrap() function
- bugfix: parameter mismatch in error message for random() function
- bugfix: divide by zero if max() function was provided zero
- bugfix: invalid mutex handling in omfile async write mode
- bugfix: fix inconsistent number processing
- bugfix: timezone() object: fix NULL pointer dereference
- bugfix omfile: memory addressing error if very long outchannel name used


(fhajny)