[mxe-octave] cairo based and lua/tikz terminals supports of gnuplot build in mxe-octave

[Tatsuro MATSUOKA]

Hello

Current gnuplot built in mxe-octave system only supports built-in terminals.
The cairo based and lua/tikz terminals are not included.
(For native build for linux, qt terminal supported because qt-4 is built in 
mxe-octave)

The gnuplot graphics_toolkit supports the cairo based and lua/tikz terminals.

https://fossies.org/dox/octave-4.0.2/____gnuplot__print_____8m_source.html


Of course, full version of gnuplot is easily available for windows, MacOSX, 
Linux, BSD or other systems.
Therefore set of gnuplot_binary to the full featured gnuplot installed outside 
of octave.

However, this situation is not friendly for non-experienced users.

Two options are considered.

1. State of mxe-octave will not be changed. Instead instructions of using 
external gnuplot are described in the Wiki.

2. The mxe-octave will be changed for gnuplot to be built with cairo based 
terminals and lua/tikz terminal.
Of course, this requires additional libraries to the mxe-octave system.

Option 1 is easy so that I will made a description on octave for windows wiki 
and MXE wiki.
After I will finish it I will ask check and revise here because my English is 
poor.

For option 2, I would like to hear the opinion from the maintainer of the 
mxe-octave.

Tatsuro