Simplify hash function to a single multiplication

More than likely the compiler will do the three operation breakdown we
had here before (2 shifts + subtraction), but let the compiler do the
optimizations and make the actual operation more obvious. This actually
slightly shrinks the function binary size, likely due to instruction
reordering or something.

Signed-off-by: Dan McGee <dan@archlinux.org>

lib/libalpm/util.c

@@ -1145,7 +1145,7 @@ unsigned long _alpm_hash_sdbm(const char *str)
 		return hash;
 	}
 	while((c = *str++)) {
-		hash = c + (hash << 6) + (hash << 16) - hash;
+		hash = c + hash * 65599;
 	}
 
 	return hash;