Dead code cleanup: crypto/*.c, x509v3, demos

Some of the #if 0 code in demo's was kept, but given helpful #ifdef
names, to show more sample code.

Reviewed-by: Andy Polyakov <appro@openssl.org>
diff --git a/demos/bio/server-arg.c b/demos/bio/server-arg.c
index 1d0e1db..7ba54db 100644
--- a/demos/bio/server-arg.c
+++ b/demos/bio/server-arg.c
@@ -72,7 +72,7 @@
         ERR_print_errors_fp(stderr);
         goto err;
     }
-#if 0
+#ifdef ITERATE_CERTS
     /*
      * Demo of how to iterate over all certificates in an SSL_CTX structure.
      */