bind: fix link-local addresses scoped with interface names

If bind's configure can't find if_nametoindex(), it only lets you use
numeric interface ids (fe80::1%5) instead of interface names
(fe80::1%wan0) to scope link-local addresses.  At the suggestion of
Alan Coopersmith, update configure.ac to search for if_nametoindex in
libsocket.

Also along for the ride, to fix tests:

1) unexport SHELLOPTS to avoid libtool wrapper failures

2) Clear LD_B_DIRECT; direct binding of bind's shared libraries breaks several
of the self tests.

3) Fix how we set the timezone to GMT in one of the tests.

4) When adding test ipv4 addresses to lo0, use a /32 prefix len so that
it doesn't default to a /8.