Now when an error in formatting happens, it never outputs anything and
doesn't override the file when working inplace.
Additionally dfmt is no longer able to fail in the middle of a file, as
now we first write everything to a buffer and only if everything was
successful, that buffer is printed to stdout or written to the inplace
file.
This should also guard against segfaults with inplace file formatting
erasing parts of the file, as well as the user thinking it was
successful, even though dfmt didn't finish properly.
WebFreak001
BBasile
skl131313