compat/fsmonitor/fsm-listen-win32: implement FSMonitor backend on Win…

…dows

Teach the win32 backend to register a watch on the working tree
root directory (recursively).  Also watch the <gitdir> if it is
not inside the working tree.  And to collect path change notifications
into batches and publish.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>