S9 LIB  (string-digest string)          ==>  integer
        (string-digest string integer)  ==>  integer

Create a digest of the given string and return it. If specified,
INTEGER determines the maximum size of the digest (2^INTEGER).

CAVEAT: This procedures uses a simple non-cryptographic BSD
sum-style algorithm. It should be replaced with a function
generating more unique digests.

The maximum digest size defaults to 2^32.

(string-digest "hello")  ==>  2107915172
