Properly format nested conditional operators.

Before:
bool aaaaaa = aaaaaaaaaaaaa //
                  ? aaaaaaaaaaaaaaa
                  : bbbbbbbbbbbbbbb //
                  ? ccccccccccccccc
                  : ddddddddddddddd;

After:
bool aaaaaa = aaaaaaaaaaaaa //
                  ? aaaaaaaaaaaaaaa
                  : bbbbbbbbbbbbbbb //
                        ? ccccccccccccccc
                        : ddddddddddddddd;

llvm-svn: 183007