Merge branch 'sgunmap2' of https://github.com/vincentkfu/fio
* 'sgunmap2' of https://github.com/vincentkfu/fio:
docs: update HOWTO and manpage for sg trim support
testing: add test scripts for sg ioengine
engines/sg: move asserts and debug statements behind a debug flag
engines/sg: add cmdp and dxferp for trims to sg error string
engines/sg: support trim operations via the UNMAP command
stat: add IO submit and complete depths to JSON output
ioengines: have ioengines with commit do own io accounting for trims