add -lgdi32 to linker libraries on windows platform

[John W. Eaton]

On 30-Jan-2009, Benjamin Lindner wrote:

| as octave 3.1.x now uses calls of the windows GDI subsystem 
| (GetDeviceCaps() in display.cc), -lgdi32 should be added to linker 
| libraries.
| (As octave is still a console application, -lgdi32 is not included by 
| mingw's gcc by default)
| 
| I had a look at the configure code, and found a suitable - and hopefully 
| appropriate - place to add -lgdi32.
| 
| Please see the attached changeset
| 
| Might this also concern a cygwin build?

If the X11 libraries are available at build time, then the code in
display.cc will only work properly if the X server is running and
DISPLAY is set when Octave starts.  Is that a reasonable assumption
for someone who wants this particular graphics feature to work on a
Cygwin system?

Anyway, I applied the patch.

Thanks,

jwe