Comment about MaxAllocSize was not updated when the TOAST-header macros
were replaced in 8.3 "varvarlena" changes. Per report from Frederik Ramm.
* be summarily denied.
*
* XXX This is deliberately chosen to correspond to the limiting size
- * of varlena objects under TOAST. See VARATT_MASK_SIZE in postgres.h.
+ * of varlena objects under TOAST. See VARSIZE_4B() and related macros
+ * in postgres.h. Many datatypes assume that any allocatable size can
+ * be represented in a varlena header.
*
* XXX Also, various places in aset.c assume they can compute twice an
* allocation's size without overflow, so beware of raising this.