method, WT_CONNECTION::configure_method.
For some reason I can'quite figure out, this set of changes made lint run a
bunch better on some sources, and showed up a few different uninitialized
variables in error paths. Got me why, but they're real, and I fixed them.
a new function wiredtiger_extension_api(WT_EXTENSION_API **pp).
Write some WT_EXTENSION_API documentation.
Remove WT_SESSION::msg_printf, add a new msg_printf extension function
instead, convert test/format to use it.
Quit using __UNUSED in the extension code, use explicit (void) casting,
it's cleaner.
