+ /* If the list contains U+0000, that element is part of the header,
+ * and should not be counted as part of the array. It will contain
+ * 0 in that case, and 1 otherwise. So we could flop 0=>1, 1=>0 and
+ * subtract:
+ * SvCUR_set(invlist,
+ * TO_INTERNAL_SIZE(len
+ * - (*get_invlist_zero_addr(inv_list) ^ 1)));
+ * But, this is only valid if len is not 0. The consequences of not doing
+ * this is that the memory allocation code may think that 1 more UV is
+ * being used than actually is, and so might do an unnecessary grow. That
+ * seems worth not bothering to make this the precise amount.
+ *
+ * Note that when inverting, SvCUR shouldn't change */