Convert bulk CTR and CBC selftest functions in Camellia to generic selftest helper functions

* cipher/Makefile.am (libcipher_la_SOURCES): Add cipher-selftest files.
* cipher/camellia-glue.c (selftest_ctr_128, selftest_cbc_128): Change
to use the new selftest helper functions.
* cipher/cipher-selftest.c: New.
* cipher/cipher-selftest.h: New.

Convert selftest functions into generic helper functions for code sharing.

[v2]: use syslog for more detailed selftest error messages

• Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>