Add PHP_INT_MIN for PHP older than 5.6

[StudioMaX]

Fix for 4a09bdb

[JamesHeinrich]

I had removed that deliberately since various sources indicated that PHP_INT_MIN was introduced in PHP v5.1.0 (e.g. https://3v4l.org/T0pZA#v5.1.0, although I can't find any explicit mention of PHP_INT_MIN anywhere in the official PHP5 changelog) and getID3 v1.9+ is listed as requiring PHP 5.3.0+
But I suppose it does no harm having that code left in there just in case.

[StudioMaX]

Actually, you're checking the constant PHP_INT_MAX which was introduced a long time ago and not PHP_INT_MIN.
But I noticed a mistake - this constant wasn't even introduced in PHP 5.6, but in 7.0. But there's probably no point in fixing the comment in the code.
https://3v4l.org/J56Vt

[JamesHeinrich]

Well that explains why I couldn't find mention of it on the PHP5 changelog.
It is on the v7.0.0 release notes https://www.php.net/ChangeLog-7.php
Added PHP_INT_MIN constant.

Updated comment in 4d4fdf4