Remove pre PHP 5.4 documentation

Hi all,

I propose to remove all pre PHP 5.4 documentation from the manual,
basically like we did with pre PHP 5.0 docs years ago.  I don't think
that there is much need to document the behavior of such old versions,
and in my opinion, almost everybody (writers and readers alike) would be
better off without these documentation parts.  We could also remove
documentation regarding extensions which are unbundled as of PHP 5.4.0
(e.g. ext/sqlite).

Thoughts?

Thanks,
Christoph