refer to our own h_errno so we don't fetch the libc one

avoid copying most of libc (except gethostent_r, which unfortunately
adds a resolver dependency) by callling the internal nsswitch functions.

provide the symbols sethostent.c in libc is missing.

modernize, comment out dead code, amend gethostbyaddr prototype.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22268, verified by myself.

Add definitions for weak aliases so that libhack functions
are actually linked instead of libc ones on ELF systems.
Fixes install/13050 and install/13153.

Sync with gethostbyaddr() declaration change in <netdb.h> rev. 1.21;
from <lha@stacken.kth.se> in PR misc/12775.

Deal with name space issues after libc/net updates.

Warnsify.
Add reduced version of getcap routines, so sysinst need not drag in
the database goop via libtermcap.

bcmp->memcmp

Minor cleanup

Add some utilities all ports might use in a ramdisk root.