Allow proxy certs to be present when verifying a chain

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Stephen Henson <steve@openssl.org>
diff --git a/apps/opt.c b/apps/opt.c
index d694fe1..f72ac64 100644
--- a/apps/opt.c
+++ b/apps/opt.c
@@ -580,6 +580,9 @@
     case OPT_V_NO_CHECK_TIME:
         X509_VERIFY_PARAM_set_flags(vpm, X509_V_FLAG_NO_CHECK_TIME);
         break;
+    case OPT_V_ALLOW_PROXY_CERTS:
+        X509_VERIFY_PARAM_set_flags(vpm, X509_V_FLAG_ALLOW_PROXY_CERTS);
+        break;
     }
     return 1;