Tools.*.features: Fixed some feature checks.

Adds "Crypto.AES.GCM" and "Crypto.ECC.Curve" to Tools.Install.features.

Replaces the check for (the nonexistant) "Crypto.GCM" with "Crypto.AES.GCM"
in Tools.Standalone.features.
Gdbm: Fixed minor leak on exit.

The Gdbm.Iterator program leaked on exit.