NASA cygwin approach

[marco atzeri <marco.atzeri@gmail.com>]

As found on HEASOFT compiling instructions:
http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/

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2) Run setup.exe

    Choose a download source, root directory, (default text file type =
unix), local package directory, connection type, and download site (for 
example, ftp://ftp.nas.nasa.gov), and then select packages.

* Important: the default package selections are insufficient for using
HEASOFT. PLEASE READ THE FOLLOWING CAREFULLY:

Once you have reached the "Select Packages" window, the top-most line
will look something like this:

+All () Default

But by default, not all of Cygwin is installed. You should click the
arrowed circle (or the word "Default") in the first line beside "+All"
until it says "Install" instead of "Default" (one click should do it),
i.e. the top line should then look like this:

+All () Install

This will install all of Cygwin. In the past, we have suggested a set
of required packages for building or using HEASOFT, but as the contents
of Cygwin packages seem to change regularly, we strongly recommend that
you install everything to avoid missing any necessary items.

If you experience problems during the Cygwin setup, please check the
resources available at the Cygwin site:

http://cygwin.com/faq/ (Cygwin FAQ)
http://cygwin.com/lists.html (Cygwin mailing lists)
http://sources.redhat.com/cygwin/cygwin-ug-net/ (Cygwin User's Guide)
http://www.cygwin.com/cygwin-ug-net/setup-net.html (help with setup.exe)
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Heasoft is a large package but suggesting to install all cygwin
seems a bit too drastic....

Marco