sys:crypto: put ciphers into one module

Makefile.dep

examples/ccn-lite-client/Makefile

examples/ccn-lite-relay/Makefile

sys/Makefile

sys/Makefile.include

sys/crypto/3des.c

sys/crypto/3des/Makefile

sys/crypto/Makefile

sys/crypto/aes.c

sys/crypto/rc5.c

sys/crypto/rc5/Makefile

sys/crypto/sha256.c

sys/crypto/sha256/Makefile

sys/crypto/skipjack.c

sys/crypto/skipjack/Makefile

sys/crypto/twofish.c

sys/crypto/twofish/Makefile

tests/test_sha256/Makefile