Added an ability to detect mouse events generated from touch events

[KivApple]

Fix for #1265

[Cobrand]

I think it should be a method and not a variable inside the enum. This is something you can "generate" from the struct itself, so it's more appropriate to use a method is_touch(). Also, it's a breaking change since we would add a variable to quite a lot of variants, which I'm not really a fan of.

[KivApple]

I see the problem in the fact that is_touch has some meaning only for few enum variants (obviously which are related to mouse events), but it will be defined for the whole enum.