Log Message:
Update TeXmacs to 1.0.0.23.

Changes since 1.0.0.15:
* Hacky support of numbers in equation arrays (1.0.0.23).
* Some little improvements in the LaTeX input filter (1.0.0.23).
* Cleanups by David Allouche, mainly in menu.scm (1.0.0.23).
* Support of the Finnish language (1.0.0.22).
* Improvements in the German dictionary (1.0.0.22).
* Temporary fix for problem with g++ 3.2 (1.0.0.22).
* Fixed problem with Guile 1.6 (1.0.0.22).
* Several minor bugs have been fixed (1.0.0.21).
* Low level support of elementary graphics (1.0.0.21).
* The online documentation system becomes default (1.0.0.20).
* New algorithm for the computation of table borders (1.0.0.20).
* Entering Greek letters as variants of normal letters (1.0.0.20).
* Applied many small patches from David Allouche (1.0.0.20).
* Creation of a made-by-TeXmacs tag (1.0.0.20).
* Updated interface for Axiom (1.0.0.20).
* Very simple browsing through help (1.0.0.19).
* Page breaks before (1.0.0.19).
* Cleanup in base.scm by David Allouche (1.0.0.19).
* A very rudimentary interface for GNU Octave (1.0.0.18).
* Several minor bug corrections (1.0.0.18).
* The packages number-europe and number-long-article can be used to
  customize the numbering conventions (1.0.0.17).
* Automatic completion support for computer algebra systems (1.0.0.17).
* Automatic completion using tab (1.0.0.17).
* Added content-based tags to Text menu (1.0.0.16).
* Improvements in the LaTeX to TeXmacs converter for reimporting
  documents which were previously exported (1.0.0.16).

I've also changed the default location of documentation files to the
standard place (providing a symlink for compatibility). It is hard (or at
least seems to me) to make TeXmacs recognize the documentation in the new
place without the symlink.

This closes my own PR pkg/18495 which provided an update to 1.0.0.17.

Reviewed by wiz.