[RFC] adding support for md5

I'd like to solicit some comments about implementing support for md5 as a hash function that could be determined at runtime by the user during a project init-db. md5, which I implemented as a configurable option in my own tree, is a 128-bit hash that is slightly more recognized than sha1. Likewise, it is also available in openssl/md5.h just as sha1 is available through a library in openssl/sha1.h. My patch to move the hash name comparison was a step in this direction in isolating many of the particulars of hash-specific dependencies.

		David