Extending round() to handle fraction part up/down

Hi, There's a PR https://github.com/php/php-src/pull/1658 about the topic. The implementation adds the ceil()/floor() equivalent for the fraction part of the float to the round() function. The PR sits there for long, the change itself looks useful and self-contained, the current behaviors are not changed. I would like to handle it on my next time frame and put it into master, if there is no objection. If someone is interested to check and give a comment, please do. Thanks Anatol