Merge branch 'packet-libfuzzer' into 'master'

LibFuzzer support

This changeset contains:

- support for compiler sanitizers and sanitizer coverage in configure
- support for LibFuzzer
- fuzzy test for packet based on LibFuzzer
- fix for NAPTR RR parsing (found by LibFuzzer)
- limit for maximal number of RRs in a parsed packet

See merge request !460