configure.ac: Add "--with-pdfdir" configure option, which defines pdfdir variable.

* configure.ac: Add "--with-pdfdir" configure option,
which defines pdfdir variable.
* Makefile.def (target=fixincludes): Add install-pdf to
missing targets.
(recursive_targets): Add install-pdf target.
(flags_to_pass): Add pdfdir.
* Makefile.tpl: Add pdfdir handling, add do-install-pdf
target.
* configure: Regenerate
* Makefile.in: Regenerate

From-SVN: r122467