New extension for hardware accelerated crc32c

Hi, I recently contributed a crc32c implementation to PHP's hash function <https://github.com/php/php-src/pull/3913>. However, I wanted to get hardware acceleration, and support older versions of PHP. So I wrote a new extension that uses github.com/google/crc32c, which utilised hardware acceleration on modern intel CPUs. My quick benchmark shows: CRC32_PHP 12.27 MB/s (pure php solution) CRC32_Builtin 468.74 MB/s (my pull request above) CRC32C_Google 24,684.46 MB/s (using new extension) I'm in the process of open sourcing my code (I have to jump though some hopes at my day job), but soon after I would like to publish the pure PHP implementation to packagist, and the compilable extension to pecl. Per the account request guidelines <https://pecl.php.net/account-request.php>, I'm reaching out to say hello. A quick note about myself, I've been a avid contributor to open source for a decade, but I haven't touched PHP recently. I have far too many project on my github <https://github.com/bramp>. I also work at Google as a Cloud Storage (GCS) SRE, and while my interest in crc32c was to improve the GCS API support, I'm doing this as 20% instead of my main duties. thanks Andrew