Provide gnuplot through BinaryBuilder artifacts

[ViralBShah]

Not sure how difficult it might be, but it would be useful to provide the gnuplot binaries as artifacts.

[gcalderone]

It would definitely be useful, but I guess the difficulties are well beyond my capabilities.

The amount of OS / libraries / version combinations is just too high. To give an idea, on my GNU/Linux ldd reports 94 shared libraries depdencies:

~> ldd /usr/bin/gnuplot | head
	libreadline.so.8 => /usr/lib/libreadline.so.8 (0x00007f37f3844000)
	libgd.so.3 => /usr/lib/libgd.so.3 (0x00007f37f37da000)
	libm.so.6 => /usr/lib/libm.so.6 (0x00007f37f3658000)
	libpangocairo-1.0.so.0 => /usr/lib/libpangocairo-1.0.so.0 (0x00007f37f2d5d000)
        ...

Even trying to compile static executables would be too demanding for me...

[ViralBShah]

All of GTK and Cairo is already available in BB. Just noting here for anyone who may be interested.

[gcalderone]

OK, and any attempt to provide a PR on this topic would be very welcome.