myproxy-init and grid-proxy-init fail when using ECDSA signed certificates. #249

An ecdsa-with-SHA384 signed cert gives this error:

Error: Couldn't create proxy certificate.
       grid_proxy_init.c:909: globus_gsi_proxy: Error with OpenSSL's BIO handle: Certificate's signing algorithm not supported by OpenSSL

because X509_get_signature_nid() returns the certificate's signature algorithm OID and returns NULL for ECDSA signature OIDs.

To reproduce:

1. Obtain a user certificate signed with ecdsa-with-SHA384 (or any ECDSA variant).
2. Run grid-proxy-init or myproxy-init -d -a -v.
3. Observe the failure above.

See PR #248 for an AI assisted fix.