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-fuzzer switch.

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

When running `make` ithhis creates these binaries in `sapi/fuzzer/`:
* php-fuzz-parser - fuzzing language parser
* php-fuzz-unserialize - fuzzing unserialize() function
* php-fuzz-json - fussing JSON parser
* php-fuzz-exif - fuzzing exif_read_data() function (use --enable-exif)