Fix missing @clicksequence problem with older Texinfo versions. The @clicksequence command was introduced in Texinfo 4.12, which a lot of users do not yet have. This commit fixes the problem by detecting whether makeinfo supports @clicksequence and, if not, defining a macro for it as a substitute. We also need support for @clicksequence in texinfo.tex. It is possible to detect whether @clicksequence is defined using TeX code and, if not, define a TeX macro for it. However, I'm not sure how to do that. So this commit instead adds a known-good texinfo.tex to the source tree, which should have the same effect.
Rewrite automake rules for internationalisation files. I got fed up with battling against the Makefile which gettext provides. So I rolled my own instead. This change provides the following advantages over previous situation: * It doesn't use recursive calls to $(MAKE). * Merged and unmerged po files are properly seperated into the buildir and sourcedir respectively. Consequently, po files get updated only when we really want them to be, and not (potentially) on every commit. * The .pot file (and consequently the .po and .gmo files) now properly depend upon all the distributed source files. There is no need to run "make -f Smake" to make it aware of new files. * There's no more need of "timestamp" files. * Potentially it's easier to add per-source-file options when generating the .pot file. (and thus avoid warnings about unrecognised extentions.