valgrind: ignore ldso and more libz errors

valgrind: ignore ldso and more libz errors

On some Linux systems, we get a host of Cond and Addr errors
from calls to dlopen that are caused by nss modules. We
should be able to safely ignore anything happening in
ld-*.so as "not our problem."

[Johannes: I added some more... unfortunately using valgrind 3.4.0 syntax]

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>