make it installable in web sub directory

[peterdd]

The global $basedir configuration is currently not used across the sources.

This PR fixes it by using the base href tag and fixing the links.

[peterdd]

There is one thing that may be annoying: When using the base-tag, relative links like <a href="#section3">Section 3 Title</a> a request to server is done instead just jumping to the position of the target id in the document without additional http request.

Wouldn't this make the base tag quite useless?

Need to research when and why this odd behavior was added/changed in HTML4/5 standards ..

[nikic]

Not sure it's worthwhile to support this. Nowadays a root URL is just a php -S localhost:8000 -t www away.

[peterdd]

I am just testing the php.net programs with apache http server in vagrant boxes, sister programs like https://pear.php.net/bugs/ use also a web sub directory.

And there is this configuration available in the sources, so made it somehow work.

So that was the motivation.

[derickr]

bugs.php.net is no longer really used, and hence, we're sunsetting it. Due to that, I don't think it makes sense to merge this patch, which also has conflicts.