Now setting environment variable nodosfilewarning to True for
Windows / Cygwin, otherwise we get annoying warnings like this:

DOS>ssh-keygen -yl -f "C:\Documents and Settings\Administrator\.ssh\MassiveLauncherKey"
cygwin warning:
  MS-DOS style path detected: C:\Documents and Settings\Administrator\.ssh\Massi
veLauncherKey
  Preferred POSIX equivalent is: /cygdrive/c/Documents and Settings/Administrato
r/.ssh/MassiveLauncherKey
  CYGWIN environment variable option "nodosfilewarning" turns off this warning.
  Consult the user's guide for more details about POSIX paths:
    http://cygwin.com/cygwin-ug-net/using.html#using-pathnames
2048 65:e6:2a:62:48:27:2a:21:42:6b:78:3f:b6:8c:fa:37   MassiveLauncherKey (RSA)