binject: a test module that allows direct injection of BIOs to a queue

binject: a test module that allows direct injection of BIOs to a queue

Not at all tested, and there's still some things that need to be
fixed up (it's a morning hack-up so far). The idea is a lower level bsg
and one that works with BIOs and not requests, to allow inserting
barriers and discards and other directly formed BIOs to test a driver.

It could also be useful as a high performance IO test tool, since
the overhead should be much lower than eg O_DIRECT.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>