Stop keeping doc/emacs/emacsver.texi in the repository
* configure.ac (doc/emacs/emacsver.texi): Generate it.
* make-dist (doc/emacs/emacsver.texi) [update]: No longer check it.
* doc/emacs/Makefile.in (top_srcdir, version): New, set by configure.
(doc-emacsver): New rule.
(bootstrap-clean, maintainer-clean): Delete emacsver.texi.
(emacsver.texi.in): Rename from emacsver.texi.
* admin/admin.el (set-version): No need to update doc/emacs/emacsver.texi.
(make-manuals-dist-output-variables): Add top_srcdir.
(make-manuals-dist--1): Handle @version@ specially.
* .bzrignore: Add doc/emacs/emacsver.texi.