clang-format: Fix bad line break with pointers to members.

Before:
  void f() {
    (a->*
     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)(aaaa,
                                           bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
  }

After:
  void f() {
    (a->*aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa)(
        aaaa, bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb);
  }

Also add missing test case.

llvm-svn: 186583