Add partial implementation for tracking dirty pages in cache.
Merge branch 'develop' into trickle
Fix tracking of dirty pages. Add statistics for dirty pages.
Merge branch 'develop' into trickle. Manual.

Conflicts:
	dist/stat_data.py
	src/include/extern.h
	src/include/stat.h
	src/include/wiredtiger.in
	src/support/stat.c
	test/format/wts.c
Remove testing change to example code.
Simplify and speed up the test_compress test, add a test run without
compression (better testing of no compression than "nop").
Move the write-generation out of the block header and into the page
header, and maintenance of the write-generation out of the block code
and into the btree code, the write-generation really shouldn't be the
block manager's problem.  This includes:

    moving the write-generation from the block manager's checkpoint
cookie and into the metadata file as a configuration string for the
checkpoint itself;

    adding functions to get/free a checkpoint structure (WT_CKPT), now
called from the btree-open routine (it's a minor simplification of the
connection code and minor additional complexity in the btree code), and
generalize the checkpoint structure load/unload code, it's now called
from more than one place.
Fix a bug I just introduced: I can't use WT_NOTFOUND to flag an existing
entry lacking a checkpoint, it has to be a side-effect.
I introduced a memory leak: free the checkpoint structure's memory,
even if we're not opening a checkpoint ourselves (salvage, verify,
or upgrade).
Merge pull request #383 from wiredtiger/test_compress

Simplify and speed up the test_compress test.
Account for pages that are dirty as they are read (e.g., internal pages with references to deleted leaf pages).
whitespace
Remove statistics that were added for debugging.
Add validation step for cache dirty counts into diagnostic build.
Revert change to increase cache size in test/format.
Update default dirty target in API so the functionality is disabled by
default.
Merge branch 'develop' into generation
index_meta column_meta and format_meta, but format_meta also includes
column_meta: remove the explicit include of column_meta.

session.create includes table_meta (defined as format_meta and
table_only_meta), plus file_config which also includes format_meta,
change to include table_only_meta instead.
Merge branch 'develop' into generation
Don't drop core if the line (a value) has no contents.
Don't drop core if the line (a value) has no contents.
Merge branch 'develop' into generation
Handle empty sources, that is, "source," or "source=," in the config
string means we don't have a valid source.