This patch helps support an extension of Bruce Ravel's gnuplot-mode to provide context-sensitive documentation lookup for Gnuplot scripts (see https://github.com/bruceravel/gnuplot-mode/tree/context for details).
It patches doc2texi.el to create an Emacs Lisp file of documentation strings extracted from the syntax description in gnuplot.doc. Gnuplot-mode can then optionally display these strings as automatic one-line documentation while editing, and pop up the full syntax description on request.
The generated Elisp file (gnuplot-eldoc.el) has a header with the Gnuplot licensing terms, and indicating that it is not designed to be edited by hand.
Also patches the necessary Makefiles and configure scripts to compile and install the ElDoc strings file in the system site-lisp directory.