On arrays starting with a negative index

Hi internals, I've prepared a PR (https://github.com/php/php-src/pull/2383) that would change the current behavior of arrays when the first index is a negative integer. The main goal is to make the result of array_fill more in line with what you would expect if the start_index is a negative integer. However, the current (and historical) result is properly documented on the array_fill page. I would like to hear your feedback about this change and if you feel this warrants an RFC. Best regards, Pedro Magalhães