Remove adapter PhpCode

[marc-mabe]

... because it's using eval.

It's only useful for testing/debugging but to dangerous to use for wrong purpose.
Because of that I propose to remove this adapter as it's also really simple to write it byself in case someone really needs it.

See #5

PS: The serializer can't use PHP's opcache as that would be another possible use as pointed out by @Ocramius - but as told it cant be done by serializer component and would live better in zend-cache.

[weierophinney]

This repository has been closed and moved to laminas/laminas-serializer; a new issue has been opened at laminas/laminas-serializer#1.