Reject multidimensional arrays in marshaled members

[radekdoulik]

trafficstars

Based on https://github.com/xamarin/java.interop/pull/351/files#r208002273, we should reject marshaled members with multidimensional C# arrays.

jnimarshalmethod-gen looks like a good place to do it.

[jonpryor]

It doesn't need to just be [Export] members, it needs to be all members for which we generate marshal members.

Granted, it shouldn't be possible for e.g. a virtual method override to contain multidimensional C# arrays, but if they did...we should error.

[radekdoulik]

That's right, I have updated the title and description. I think I will check it when traversing the API before generating the marshal methods.