[lmi] Use a different Cygwin mirror

[Vadim Zeitlin]

 Hello,

 As explained at http://mirror.mcs.anl.gov/ this mirror is not available to
the public any longer since 2015-02-01, so attempts to follow lmi setup
instructions now fail right at the beginning as Cygwin can't be installed
following them and install_cygwin.bat file needs to be updated to use
another mirror.

 I've verified that http://mirrors.kernel.org/sourceware/cygwin/ works
fine so you could just replace ftp://mirror.mcs.anl.gov/pub/cygwin/ with
this URL to fix the problem. I chose this mirror from the list at
https://cygwin.com/mirrors.html because it seems unlikely to cease
operating any time soon (and if kernel.org does go down, we might have
worse problems than not being able to install lmi), but it is almost
certainly not be the fastest one for you, considering that it is located
right across the country in California. It's difficult for me to find out
which one would be the fastest though, so I'll let you decide which one you
prefer to use -- but any mirror would be better than the current broken
one.

 Regards,
VZ