Windows build fixes

Windows build fixes

Bruce writes:

SIGUSR1 isn't defined on Windows so I've defined it.

Also, MSI packages need a version string of x.x.x.x where x is between 0
and 65535 so we can't include the git hash. It's easier just to go back
to hard-coding the version for now, and I'll update it (and the product
GUID) when I create a new package (it doesn't need checked in each
time).

Also, Cygwin doesn't like $(SHELL_PATH) but $(SHELL) seems to work -
does $(SHELL) cause a problem on other platforms?

Signed-off-by: Jens Axboe <axboe@kernel.dk>