Fast parser should warn about using ellipses with other function arguments

[ddfisher]

For this function:

def f(x, y, z): # type: (..., int) -> None
     pass

The old parser would give the warning: Ellipses cannot accompany other argument types in function type signature., whereas the fast parser gives the less helpful Type signature has too few arguments.

The fast parser should look for ellipses args and give a special-cased better error message.