Re-word a comment for clarity.
If we match keys in the internal page, then instantiate an empty leaf
page and so never set the comparison value during the search of the leaf
page, we'll end up with the comparison value set to 0 from the internal
page search, and the we'll be all sorts of sad.  Reference #437.
Instead of skipping eviction of empty pages, set the parent page's WT_REF to
WT_REF_DELETED, that way we can discard the page.  Reference #437.

If we instantiate an empty page (and it's really empty, for example, it
was instantiated as part of a search), and we eventually discard it
without modifying it, we have to reset its WT_REF status to empty, not
to on-disk, because it has no disk address.

Don't cache a reference to the page's modify structure, the call into
reconciliation can swap out the page's modify structure for a new one.
typo
Merge pull request #438 from wiredtiger/empty-evict

Allow empty pages to be evicted from cache independent of their parents.
When generating an empty in-memory page to satisfy a search into a deleted key range, mark the new page with WT_PM_REC_EMPTY so a concurrent checkpoint will skip over it.
refs #437
The page returned from the walk of the cache will always be in state
WT_REF_EVICT_WALK, we don't need to check for it.
src/btree/bt_read.c: function with return after a jump to an error label
function @ line: 64