Windows updates

- Remove files which are present in a minimal/default installation
  of Cygwin but which aren't needed to run fio. These include man pages,
  awk, groff etc.

- Remove CR from Makefile.Windows in order to maintain consistency with
  the rest of the files.

- Improve the documentation given when starting the FIO environment.

- Rename Cygwin.bat to FIO.bat and add FIO.lnk which is a shortcut to
  FIO.bat configured with QuickEdit and a larger window.

- Reformat install.wxs and move documentation from
  Program Files\FIO\usr\share\doc to Program Files\FIO.

- Restore $(EXTFLAGS) in the Makefile's to enable extra flags to be
  passed on the command-line.

- Remove os/windows/fio.sh which was an experimental way of setting up
  the Cygwin environment that has been replaced with FIO.bat.

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