cipher: Fix possible NULL dereference.

* cipher/md.c (_gcry_md_selftest): Check for spec being NULL.
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Also removed left-over code in unused file cipher/test-getrusage.c.

Found by Hans-Christoph Steiner with cppcheck.
pubkey: Re-map all deprecated RSA algo numbers.

* cipher/pubkey.c (map_algo): Mape RSA_E and RSA_S.