If the child is blocking SIGPIPE, unblock it so that we can handle any that
get generated while we're tricking libldap into telling the server on the other
end of a dummy socket to close the connection.  Upstream #414.

diff -up nss_ldap/ldap-nss.c nss_ldap/ldap-nss.c
--- nss_ldap/ldap-nss.c	2009-12-07 20:57:33.000000000 -0500
+++ nss_ldap/ldap-nss.c	2009-12-07 20:58:56.000000000 -0500
@@ -532,8 +532,13 @@
 static void
 do_atfork_child (void)
 {
+  sigset_t unblock, mask;
   debug ("==> do_atfork_child");
+  sigemptyset(&unblock);
+  sigaddset(&unblock, SIGPIPE);
+  sigprocmask(SIG_UNBLOCK, &unblock, &mask);
   do_close_no_unbind ();
+  sigprocmask(SIG_SETMASK, &mask, NULL);
   _nss_ldap_leave ();
   debug ("<== do_atfork_child");
 }