Support for a new configuration option, file_extend, that extends the file
in chunks instead of doing it a block at a time.
Merge branch 'develop' into file-extend
When unloading the live checkpoint, discard any extended blocks so files
don't stay longer than they need to be.  This means we truncate file on
both "open" and "close", but that doesn't seem too awful.
Merge branch 'develop' into file-extend
Merge branch 'develop' into file-extend
Merge branch 'develop' into file-extend
Fix an off-by-one error in the transaction used for eviction.  We track the oldest ID that can *not* be written.
Snapshots (including eviction) *should* include the last committed transaction.
Merge pull request #537 from wiredtiger/eviction-isolation

Fix an off-by-one error in the transaction used for eviction.
Only track whether eviction is stuck if the cache is full.
minor rephrasing so two patterns match
Merge branch 'develop' into file-extend
Change file_extend syntax from file_extend=(type=[data,log],size=XXX)
to file_extend=(data=XXX,log=XXX).

Add period testing of file_extend to test/format.
Merge pull request #534 from wiredtiger/file-extend

file extension
Fix a bug where clean pages could be evicted when they contained updates required for a running transaction.
fix a comment
Include the current transaction when calculating the oldest snapshot ID.
Acquire the file-list spin lock when checking the WT_FH.refcnt during
close, there's a race across the reference count test and decrement.

Check for the name again before we link a duplicate file descriptor on
the list of open files, it doesn't cost us anything to avoid the race.
Fix ordering of application eviction so a session's read-committed transaction can't block eviction (for forced eviction of big pages).  Fix a race calculating the oldest snapshot ID required for eviction.
typo