Also, the pdf content was written in the gnuplot.log file.

Add tests

Indeed, it is not lutils fault when it occurs.

Indeed, it seems it is not supported by gnuplot anymore (at least it
is disabled in the version shipped with debian 8).

and collect the stdout lines into a list (requires sed)

Also add an entete2 command that accept multi-line comments

The rationale is  to avoid a clash on case unsensitive arch (mac os)