Rename .php3 files to .php.

*.php3:
	Rename to .php.

Makefile.common:
bin/install_webpages:
	Conform to extension change.
Start a new makefile for the web site.

Add a new makefile to build .html files from .php and .inc source files.
Unlike the previous makefile, it does not require explicit listing of
pages and sub-directories, which helps when the site is reorganised.

The new makefile does not use recursive make.
It can be invoked at the top-level like:  make -f Makefile.new

Makefile.new:
	As above.
Change the website style and menu structure.
Update menu, template.
Finish About section and adding favicon.

Move files around to fit the new structure, finish all the sub pages for
ABOUT section and adding the new favicon.
Finish Download, Contact and Documentation section
Update pages layout, style and menu.
Update style and content.
Added Homepage, fix links.
Fix banner and else.
Remove bug datebase from development.
Rename release-11.07.02.php to release.php.
Replace non-UTF-8 characters by HTML entities.
Replace .php links by .html links.
Add footer.inc as a common include file.
Delete placeholder footer text.
Replace GPL3 by GPL2 that we use in the source distribution.
Use the copyright statement from the README.
Fix banner URL.
Reword heading on About page.