On some platforms (notably FreeBSD) netinet/in.h is required
for the struct in_addr type and IPPROTO_* constants.
As this header and both required definitions are documented
in IEEE Std 1003.1, this should be safe on all systems.

some time ago gssapi.h moved to gssapi/gssapi.h, and on some systems
(e.g. FreeBSD) gssapi.h carries a deprecation #warning - which becomes
a fatal error since we're compiling with -Werror

As far as I can tell, libresolv is not needed anymore.
To avoid build breakage on systems where the resolver functions
live in libc, just remove -lresolv

FreeBSD has clang as it's primary C compiler (and often no gcc,
these days). To avoid using the "wrong" compiler (gcc installed
via ports if available), test for cc first.

as loudmouth is maintained in git, the whole concept of rcsid does
not really apply anymore - but we get warnings from -Wunused which
are promptly upgraded to errors (-Werror)

assorted minor build fixes

Changeset 74d6f24 breaks builds here (Debian Jessie), because
__res_query is not found...