Bug#764904: apophenia: FTBFS - test suite times out or has unexpected failures

[Edmund Grimley Evans]

Some good news: the code doesn't seem to need a lot of changes to make
it work on arm64. I did this:

* Changed the type of the local variables to which the value returned
  from fgetc, getopt or get_next is assigned from char to int.

* Made get_next return int instead of char, and, to make it return EOF
  when it should, set buffer[len] to (char)-1 when len < bs and
  instead of returning buffer[(*ptr)++] assign that to a new local
  variable r and return (r == (char)-1 ? EOF : r). (In a
  ISO-8859-1-encoded file 'ÿ' will be interpreted as EOF, but that was
  presumably already the case. If you really want all characters to be
  correctly distinguished then you will have to add an out-of-band way
  of denoting EOF.)

With those changes, apophenia passed its tests on arm64.