[BuildTools] --enable-doscompile

[Andreas Waechter]

Hi,

It seems that a number of people (mainly Ipopt users) got confused with 
the changed behavior of --enable-doscompile.  I would like to change it so 
that if one works on Cygwin, the default for this is not "no", but mingw, 
so that executables will be able to run without the Cygwin dll.  Also, if 
the AMPL solver executable is not compiled with -mno-cygwin, it seems that 
the AMPL options are not given properly to the solver executable (which is 
done via environment variables).

In case you strongly disagree with this, please let me know (and why ;), 
otherwise I will change it soon and make a new release for BuildTools.

Thanks

Andreas