New "standard" for hash functions

Rev: src/modules/_Crypto/hash_submodule.doc:1.1

src/modules/_Crypto/hash_submodule.doc

+A hash sub-module needs to implement the following Pike-functions:
+
+void update(string);		/* Add this string to the hash */
+string digest(void);		/* Get the digest, and reset the state */
+int query_digest_size(void);	/* Returns the size of the digest */
+string name(void);		/* Name of the algorithm */