* md2.c, md2.h: Added reference to RFC 1319.

* md4.c, md4.h: Added reference to RFC 1320

Rev: src/nettle/ChangeLog:1.208
Rev: src/nettle/md2.c:1.2
Rev: src/nettle/md2.h:1.2
Rev: src/nettle/md4.c:1.2
Rev: src/nettle/md4.h:1.2