Add WT_COLLATOR::customize, allowing collators to be customized for specific data sources, or with application-managed metadata.
Minor cleanups: "onpage_ovfl" is never interesting if the overflow key
has already been removed, factor that into the original test and set of
the variable.
typo, should be case 7, not 8.
no need for a WT_RET followed by a return, just return.
Fix up an incorrectly copied comment.
Simplify the row-store page merge code, track the start/stop compare
values, it makes it easer to debug.
Panic if "impossible" cases occur during the merge.
Bug, wasn't incrementing the WT_ROW reference, potentially leads to
leaking overflow pages or failure when attempting to free the same
overflow pages twice.
Bug: if we split a page into two chunks, then subsequently discarded the
chunk that didn't "own" the original backing file block, we'd free the
backing file block twice.
Now that __slvg_trk_free checks WT_TRACK_NO_FILE_BLOCKS, be more
aggressive about calling it from __slvg_merge_block_free, we can
discard more memory quicker, that way (no clue if that matters,
but it can't hurt).
Remove code to handle the case where we take the entire page when
building a row-store leaf page; it can't happen, and we assert that
fact earlier in the function.
Minor code shuffling, comment cleanup when splitting chunks, for clarity.
Add upgrading notes about the WT_COLLATOR change.
Merge pull request #1165 from wiredtiger/custom-collators

Add WT_COLLATOR::customize, allowing collators to be customized
Clarify the comment when clearing the eviction walk point: that can cause eviction, revert the flag.

refs #1160
Add a special "local" extension target that can call out to initialization functions within an application.

This will fail when attempting to run the `wt` utility, but it supports cases where extensions cannot be separate from application logic (e.g., custom collation routines).
Fix the metadata passed to WT_COLLATOR::customize
Add a page on writing WiredTiger loadable extensions, explain the special "local" usage.
Merge pull request #1174 from wiredtiger/mongo-collators

Fixes for MongoDB collators. Add support for loading extensions from application binary.
Merge branch 'develop' into add-filter-support

Conflicts:
	src/config/config_def.c
	src/include/extern.h
	src/include/wiredtiger_ext.h