Remove remaining dependence on CVS Id keyword.

Remove remaining dependence on CVS Id keyword.

* ChangeLog: For the sake of people still using CVS, don't use dollars
when mentioning Id.
* data/xslt/bison.xsl: Remove Id from header comments, where it was
unusual anyway.
* data/xslt/xml2dot.xsl: Likewise.
* data/xslt/xml2text.xsl: Likewise.
* data/xslt/xml2xhtml.xsl: Likewise.
* doc/Doxyfile.in (PROJECT_NUMBER): Don't use ID.
* doc/Makefile.am (neutralize): Remove, no longer needed.
(.x.1): Don't use neutralize.
(edit): Don't substitute for ID.
(Doxyfile): Don't define Id, and thus don't depend on ChangeLog.