Minor tweak to hostname check for Cygwin environment support

I'm pleased to say your script works perfectly on Cygwin except for the
hostname check. Under Cygwin the hostname command has no parameters and
so the "-s" option fails. However, it returns a short name by default.

Some Cygwin environments may also run into a problem due to the "cal"
program not being included, however, this can easily be fixed via
installing the util-linux package.