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
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 comment