Calling

	(hash #t 0)

kills guile with a divide-by-zero, whereas I'd have hoped probably for
an out-of-range error throw.

        * hash.c (scm_hashq, scm_hashv, scm_hash): Restrict to size>=1 rather
        than just size>=0, since 0<=hash<size cannot be satisfied when
        size==0, and such a size causes divide-by-zeros in scm_hasher.

This would be for the 1.6 branch too, it's the same there.