cygwin: src/sysdep.cc patch

[John W. Eaton]

On  7-May-2009, Marco Atzeri wrote:

| the attached patch remove the call to
| cygwin32_conv_to_full_win32_path
| from src/sysdep.cc and replace with a more standard 
| 
|    if (tmpdir.empty ())
|      tmpdir = "/tmp";
|    octave_env::putenv ("TMPDIR", tmpdir);
| 
| 
| The function was deprecated in cygwin-1.5 and has been
| removed in cygwin-1.7.
| As it was used to set TMPDIR=c:/temp that is also
| deprecated in cygwin, I see no reason to mantain it.
| 
| This solution is already implemented in the
| cygwin 3.0.x official packages.

As I recall, the original reason for using TMPDIR=C:\TEMP was so that
Octave would write tmp data files for plotting in a location that the
the Windows version of gnuplot could find.  I don't guess that matters
now since we don't use tmp files for communicating with gnuplot.
Also, the Cygwin version of Octave should probably just use Unixy
features by default and leave the Windowsy things to the native
Windows version.

But if we are just going to set the default to /tmp as on other
systems, I'd guess that the cygwin init function could simply be
removed.  Or is there some need to set TMPDIR in the environment on
Cygwin systems?

jwe