Pager links for next month are not working correctly.

Problem/Motivation

When you have a view that lists stuff and use the views_date_plugin_pager plugin for pagination.
Configure "Date identifier" to "month". The plugin works and has 2 buttons previous and next...

The problem is with the next link. Date generated for it skips a month, when a 31 days are in the current month.

It's a PHP thing coming from the following lines in the plugin:

$this->view->date_info->prev_date = clone($argument->min_date);
date_modify($this->view->date_info->prev_date, '-1 ' . $argument->date_handler->granularity);
$this->view->date_info->next_date = clone($argument->max_date);
date_modify($this->view->date_info->next_date, '+1 ' . $argument->date_handler->granularity);

Sample script to show the issue and a fix:

$date = new DateObject('2017-03-31 23:59:59');
$date2 = clone $date;
$date3 = clone $date;
date_modify($date2, "+1 month");
date_modify($date3, "last day of next month");
echo $date,' ' , $date2, ' ', $date3;

Proposed resolution

Solution inspired from here: https://derickrethans.nl/obtaining-the-next-month-in-php.html
Will work for PHP 5.3+.

Have a designated mapping for each granularity of links that will generate the previous and next link dates.
If a mapping is missing - fallback to the current behavior.

Remaining tasks

Discussion
- Do we have a minimum version supported?
- If so, should we set it to PHP 5.3+.
- How does this reflect the fact that latest supported PHP at the moment is 5.6 (as a language).

Patch etc.

User interface changes

None.

API changes

None.

Data model changes

None.