hardcopy support for gl-render and the fltk_backend

[John W. Eaton]

On 13-Oct-2009, Shai Ayal wrote:

| I attach a changeset which adds postscript output to the fltk backend,
| based on the gl-renderer and the gl2ps library
| (http://www.geuz.org/gl2ps).
| This changeset is relatively big because the gl2ps library is
| distributed as 2 files - gl2ps.c and gl2ps.h which need to be included
| in the distribution of the project using it. There is no binary
| library.
| to use :
| backend("fltk"); plot(randn(1e3,1)); print("test.eps")
| 
| Limitations (which I will try to fix in the future):
| 1. no support for images
| 2. only supports the postscript core fonts Helvetica, Times-Roman,
| Courier, Symbol, ZapfDingbats (defaults to Helvetica)
| 3. no support for bold/italic fonts
| 4. outputs only eps

I made some additional changes (mostly style fixes plus adapting to
the new build system) and checked in this patch.

Thanks,

jwe