This function claims to perform an strncat()-like operation but it does
not, it always copies the indicated number of bytes, regardless of the
presence of a NUL character (what is currently done by chunk_memcat()).
Let's remove it and explicitly replace it with chunk_memcat().
This patch fixes all the leftovers from the include cleanup campaign. There
were not that many (~400 entries in ~150 files) but it was definitely worth
doing it as it revealed a few duplicates.
