Create a new cell type WT_CELL_ADDR_LEAF, use it to mark leaf page
address cells (instead of WT_CELL_ADDR which marked either a leaf page
or an internal page); rename WT_CELL_ADDR to be WT_CELL_ADDR_INT, used
only for internal pages.

Change the address cell's type to no longer be accessible only as a
"raw" type, the unpacked "type" field now has the real cell's type.

Add code to compare parent-page cell types against child page types
during verification.
Don't perform leaf-no-overflow cell type checks for row-store internal pages,
they aren't leaf pages.
Enhance some comments -- explain why WT_CELL_ADDR_LEAF_NO isn't guaranteed
to be set if the leaf page contains no overflow items.
lint: break is unreachable after return.
Don't output the file offset on verbose, it's too much verbage.
Compaction changes: fix a bug, we were skipping internal pages if they
didn't need to be rewritten, but we can't do that, we have to read and
traverse them in order to visit all the leaf pages that might need to
be rewritten.
Drive an error return from __wt_ref_info() to the surface.
Merge branch 'develop' into page-leaf-cell
Merge branch 'develop' into page-leaf-cell
"hazard reference" -> "hazard pointer"
I'm adding more error checking to __wt_ref_info(), don't be so pessimistic.
Review all of the calls to __wt_ref_info(), ensure they handle a
successful return of no-address (addr == NULL).  I'm not 100% sure
it can happen, to be honest, but there's no reason to drop core.
whitespace
Change compaction to not block checkpoints: during the part of compaction
that views page modification/reconciliation information, compaction and
reconciliation both lock the page.
lint
Fix a path where we could return without releasing our page lock.
Didn't compile before I pushed, sadness resulted.
Merge branch 'develop' into page-leaf-cell
Change compaction into one-pass over the cache, handling both in-memory and
on-disk pages in the same pass.
Switch back to storing an index into the array of page locks rather than a direct pointer.

Backs out part of 64f087c3ab98f48924d03de0f532ef723b6430ce.