dirmngr: Use --ldaptimeout for OpenPGP LDAP keyservers.

* dirmngr/ks-engine-ldap.c (my_ldap_connect): Use LDAP_OPT_TIMEOUT.
* dirmngr/dirmngr.c (main): Move --ldaptimeout setting to ...
(parse_rereadable_options): here.

Note that this has not yet been tested. In fact a test with OpenLDAP
using a modified route got stuck in the connection attempt. Maybe it
works on Windows - will be tested later.

• Signed-off-by: Werner Koch <wk@gnupg.org>