daemon/Win32: make some functions and fields optional.

daemon/Win32: make some functions and fields optional.

inotify: Make this optional on platforms that don't have this interface.

mknod, mkfifo etc.: Make these optional on non-Unix platforms.

readdir: If d_type field is missing on the platform, set the corresponding
field to 'u'.

stat: st_blocks and st_blksize are missing on non-Unix platforms, so
set these fields to -1 in the corresponding structures.