Detect method varargs changes

[Marcono1234]

Changing a method from varargs to non-varargs is most likely a source incompatible change:

void test(int... args) {
}
// to:
void test(int[] args) {
}

Fails with the following source code:

test(1, 2);

Changing a method from non-varargs to varargs is most likely source compatible (unless I am overlooking some corner case with overloads).

Feedback is appreciated!

[Marcono1234]

Have also added this check for constructors, though the names METHOD_NOW_VARARGS and METHOD_NO_LONGER_VARARGS might be a bit misleading then. Should I rename them?

[siom79]

Released with 0.16.0.

Thanks a lot for the contribution.