eval.c:1995
static VALUE
search_iclass(self, klass)
    VALUE self, klass;
{
    VALUE k = CLASS_OF(self);

    while (k && !(BUILTIN_TYPE(k) == T_ICLASS && RBASIC(k)->klass == klass)) {
	k = RCLASS(k)->super;
    }
    return k;
}
