add error handling for fread, fwrite, and fscanf calls

use "fputs" instead of "fprintf" to avoid warning that it couldn't varify
the format string because it wasn't a string literal.

Change-Id: I1137160d28461fbac69c8e05d32ba010da491c57
Reviewed-on: https://gerrit.libreoffice.org/903Reviewed-by: Petr Mladek <pmladek@suse.cz>
Tested-by: Petr Mladek <pmladek@suse.cz>