Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

libcasper: Create a minimal cap_netdb service

Create a casper service for netdb functions.
Initially only cap_getprotobyname is implemented.

This is needed for capsicumizing sockstat.

Reviewed by: oshogbo, bcr (manpages)
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D24832