ECL build system, library name, and Cygwin

Dear all,

A feature request by Sagemath's folk seem to have fallen into oblivion. The original sourceforge request is not online anymore but the mailing discussion has been archived:

• https://www.mail-archive.com/ecls-list@lists.sourceforge.net/msg01978.html

The feature request is to change the non-standard library name ecl.dll to cygecl.dll and also to produce an import library on Cygwin.

A patch (which has been used in Sage for years) is available here:

• https://github.com/sagemath/sage/blob/master/build/pkgs/ecl/patches/implib.patch Note that the patch might also touch autogenerated files produced by autoreconf, I wrote it 4 years ago so I don't really remember...

Best, JP