[dsc] DSC release 2.6.0

[Jerry Lundström]

Hi all,

Two new DNS filters and configuration for client subnet netmask has been
added thanks to pull request submission from Manabu Sonoda (@mimuret),
see `man 5 dsc.conf` for more details.

  https://www.dns-oarc.net/files/dsc/dsc-2.6.0.tar.gz
  6f3e0036cb4a228a9f7c3ebb9d5c264d8dd21fe5a769bfae6d2ef43fac807b16

Packages are available at:

  https://dev.dns-oarc.net/packages/

New DNS filters:
- `servfail-only`: Count only SERVFAIL responses
- `authentic-data-only`: Count only DNS messages with the AD bit is set

New configuration:
- `client_v4_mask`: Set the IPv4 MASK for client_subnet INDEXERS
- `client_v6_mask`: Set the IPv6 MASK for client_subnet INDEXERS

Fixes:
- Set `_DEFAULT_SOURCE`, was giving compile warnings on some platforms
- Update `pcap-thread` to v2.1.3 for compatibility fixes
- Fix bug where extra `"` would be OK in configuration
- Eat all white-space between tokens in configuration
- Minor documentation corrections

Commits:
8a20421 Config parse quote/whitespace bug
4eb91d8 PR review and corrections
1dcdbc1 add supports statistics for DNSSEC validation resolver
        - SERVFAIL DNS message filter
        - AD bit DNS message filter
        - set custom mask for ClientSubnet
7c4ce7e Update pcap-thread to v2.1.3
f5d152c Corrected date
04f137d Prepare SPEC for OSB/COPR
402c242 Config header is generated by autotools

Cheers,
Jerry