BUGFIX: Use Object->hasMethod() instead of method_exists()

[madmatt]

This allows you to for example return a PaginatedList object from ModelAdmin::getList() without GridField failing when trying to render that list in certain circumstances.

I can't see a downside to this, a slight performance hit as it now checks for extension methods as well as the standard method_exists(), but it's only executed once per rendered GridField.

Wasn't sure if I should raise this against 3.1 or 3.2?

[tractorcow]

3.2 please. :D Sorry but 3.1 isn't really accepting minor inconvenience fixes anymore.

[dhensby]

This never made it in to core, which is a shame - @tractorcow you strict man!

@madmatt do you want to get it in to 3.2? :)

[tractorcow]

This was merged with #4728