Add skipped WT_UPDATE save/restore support for variable-length column-store
objects.  This code is mostly going away, I think, but this is the last working
(well, at least lightly tested) version before doing the general restructuring
to support raw compression.
Keep lint quiet about indirecting through NULL.
Rework skipped updates to be compatible with raw compression: save the
skipped updates in the per-page reconciliation structure, and then as
each block is defined/written, move updates inside the block's key space
to the per-block structure for eviction to instantiate.
lint