Error check X509_ALGOR_set0() in {dsa,ec}_pkey_ctrl()

Error check X509_ALGOR_set0() in {dsa,ec}_pkey_ctrl()

These are four versions of near identical code: PKCS#7 and CMS controls
for DSA and EC. The checks are rather incomplete and should probably be
merged somehow (see the Ed25519 version in ecx_methods(). For now, only
replace X509_ALGOR_set0() with its internal by_nid() version and, while
there, spell NULL correctly.

ok jca