symm/: Eliminate the remaining checked-in stubby source files.

symm/: Eliminate the remaining checked-in stubby source files.

Now that $(STUBS_SRC) actually works, use it to eliminate `safersk.c',
`sha224.c', `sha384.c', and `whirlpool256.c'.  Move test vectors to
their new homes, and modify the base files to actually run them.

Alas, the build machinery wants to ship `t/safersk' even though it's
empty, so leave it as a stub.  (Maybe...)  And the HMAC mode machinery
wants to put its test in the mode test-vector file, which is a bit
annoying.  Still, the cruft is reduced.