Add a test case for a performance regression.
Yet another rearrangement of the forced eviction code.  Now check the first time we read a page in a transaction.  That way, it shouldn't contain updates from the current transaction that prevent eviction.
Update new test case to run in a reasonable time.
Update index performance test to test combinations of file and LSM.
Merge branch 'develop' into force-evict-index
Make sure the oldest transaction ID we need always moves forward.
Simplify scans through the global table of transaction IDs.

Stop caching multiple copies of the oldest transaction ID required to stay in
memory.  In the process, fix a race that could invalidate the calculation of
the oldest ID.
refs #552
Avoid a race when updating the shared table of transaction IDs and calculating the oldest active transaction ID.
Remove a bogus assertion from transaction ID management.
Merge pull request #552 from wiredtiger/force-evict-index

Fixed forced eviction with indexes.
Add an explicit enable setting to shared_cache configuration.

It used to rely on the shared_cache configuration group being
present in
the user configuration string. This change will require applications
using the shared cache functionality to add "enable=true" to the
shared_cache configuration group.
Add upgrade documentation for new shared_cache configuration option.