symm/blkc.h, symm/hash.h: Factor out pieces of the test machinery.

symm/blkc.h, symm/hash.h: Factor out pieces of the test machinery.

This will allow a source file to include tests for a hash function or
block cipher /and/ other kinds of tests.  Possibly even for another hash
function or block cipher.

This was mostly done already for block ciphers: the remaining piece
involved making a macro to populate the test table.  But hash functions
haven't been as fortunate.

Fix the new definitions to allow non-identifier names for hashes and
block ciphers, to match the mode definitions.