Add y_hash_sdbm(), improve y_param_unique() with it.

Another option we're considering is using the (undocumented!) function lr_generate_uuid_on_buf() for this:

void y_param_unique(char *param)
{
    char buf[25];
    lr_generate_uuid_on_buf(buf);
    lr_save_var(buf, 22, 0, param); // save & trim off ==
}

That has the advantage of being one hell of a lot simpler code, and offloading the problem to windows devs ..
Disadvantage: Use of undocumented API's ..