Still looking for the best way to implement the improved
PDL::NiceSlice sourcefiltering.  Unfortunately, all the
options so far all have a gotcha of some sore to them...

Also update Release_Notes and Known_problems for the
PDL-2.004_012 CPAN developers release.

This is the start of code freeze for PDL-2.006.

In the t/plplot.t, added some logic to skip the final test on darwin.
The SVG file PLplot generates is large but valid. Also zero-padded the
names of the output files (test2.svg --> test02.svg) so they would be
in numerical and lexical order in directory listings, for debugging purposes.
In the Makefile.PL, I added some logic to remove the 'temp' executable so
that the build directory would stay clean.

No workaround in the test suite, it seems to be a rare problem.

The IMG_PTR needed to be a longlong, but was a long.  At that made all the difference.
I do not have BSD AMD64, but was getting a segfault after "ok 19" when the DESTROY
was called.  I have not removed the TODO from the gd_oo_tests.t, we should do that
after it is certain that this does not break anything for anybody else.

NOTE: the demo loading needs to be made more robust
against missing dependencies.  PDL::Graphics::Gnuplot
needs to install the demo file into the correct install
location.

…nuplot to the demos tree; group gnuplot with the other packages.