Add documentation for the C example
Add documentation for the C example

noikiy/Benchmark-PHP-HHVM-Zephir,treffynnon/Benchmark-PHP-HHVM-Zephir,noikiy/Benchmark-PHP-HHVM-Zephir,treffynnon/Benchmark-PHP-HHVM-Zephir,treffynnon/Benchmark-PHP-HHVM-Zephir,treffynnon/Benchmark-PHP-HHVM-Zephir,noikiy/Benchmark-PHP-HHVM-Zephir,noikiy/Benchmark-PHP-HHVM-Zephir,noikiy/Benchmark-PHP-HHVM-Zephir