Remove usage of "unlocked" variant of stdio print functions

Remove usage of "unlocked" variant of stdio print functions

These "unlocked" Linux Standard Base variants of standard functions
are not available on some systems that are still capable
of building Linux and ELFs.

The difference is negligible for simple printing to stdout.

POSIX also states for the similar putc_unlocked():

  These functions can safely be used in a multi-threaded program
  if and only if they are called while the invoking thread owns
  the (FILE *) object, as is the case after a successful call
  to the flockfile() or ftrylockfile() functions.

...

  These unlocked versions can be safely used
  only within explicitly locked program regions,
  using exported locking primitives.

and these precautions were never done.

Use the standard forms of these print functions.

There is inconsistent use of fputc_unlocked() with putc_unlocked(),
so consistently use the safer fputc() instead.

Signed-off-by: Michael Pratt <mcpratt@pm.me>