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() {}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181877 91177308-0d34-0410-b5e6-96231b3b80d8