Add support for method calls on primitive types in PHP

This extension implements the ability to register a class that handles the
method calls to a certain primitive type (string, array, ...). As such it
allows implementing APIs like $str->length().

The main purpose of this repo is to provide a proof of concept implementation
that can be used to design the new APIs. The switch to object syntax for
operations on primitive types is a unique opportunity for PHP to redesign many
of its inconsistent core APIs. This repo provides the means to quickly
prototype and test new APIs as userland code. Once the APIs are figured out it
will be proposed for inclusion into PHP.

Note: The ability to register type handlers from userland is just for
prototyping.

WWW: https://github.com/nikic/scalar_objects