Fuzzing SAPI for PHP

Installation

For installation put this code into a directory sapi/fuzzer inside a PHP
source tree, then run `./buildconf` and `./configure` PHP using the
--enable-fuzz switch.

You need llvm/clang's libFuzzer to be around.

When running `make` ithhis creates thee binaries in `sapi/fuzzer/`:
* php-fuzz-parser
* php-fuzz-unserialize
* php-fuzz-json

Which will use fuzzing on the language parser, the unserialize parser
and the json parser.