Break function declarations after multi-line return types.

Before:
template <typename A>
SomeLoooooooooooooooooooooongType<
    typename some_namespace::SomeOtherType<A>::Type> Function() {}

After:
template <typename A>
SomeLoooooooooooooooooooooongType<
    typename some_namespace::SomeOtherType<A>::Type>
Function() {}