Support collecting all values of valued arguments
Created by: mbaynton
Support collecting all values of valued arguments when they are specified multiple times.
So, you can make a new Option('a', null, GetOpt::REQUIRED_ARGUMENT | GetOpt::MULTIPLE_ARGUMENT). Then for
./my-script.php -a str1 -a str2
the option value for option a is an array containing all values that were provided.