* doc/share: New svn:external.
	* doc/Makefile.am: Adjust.
	Ship it.
	Fix MAINTAINERCLEANFILES.
	* doc/Makefile.doc: Rename as...
	* doc/doc.mk: this.
	Use share/ features.
	Use GNU Make features (if someone thinks that's too much to
	ask for, make it independent from share/make Makefiles).
	* doc/texi.hva, doc/texi.sty, doc/vaucanson-g.sty,
	* doc/Vaucanson-G.tex, doc/hevea.sty: Remove, they are
	in share/.
	* doc/manual/Makefile.am: Include doc.mk, it is there to be used.
	Remove the duplicate code.