handles the overlay property `display' specially, preserving it during
temporary overlay showing in the course of an isearch operation.
+** New variable `hs-allow-nesting' non-nil means that hiding a block does
+not discard the hidden state of any "internal" blocks; when the parent
+block is later shown, the internal blocks remain hidden. Default is nil.
+
+++
** `hide-ifdef-mode' now uses overlays rather than selective-display
to hide its text. This should be mostly transparent but slightly