Changes:
Do not use getprotobynumber() for protocol name resolution. Do not do
any protocol name resolution if -n is specified.
Improve errors detection in the test scripts.
Fix a segfault with OpenSSL 1.1 and improve OpenSSL usage.
Clean up IS-IS printing.
Fix buffer overflow vulnerabilities:
CVE-2017-11543 (SLIP)
Fix buffer over-read vulnerabilities:
CVE-2017-11541 (safeputs)
CVE-2017-11542 (PIMv1)