CTL_STATUS_t ctl_ms_read_char(CTL_STREAM_t s);
ctl_ms_read_char reads one character from the file f. Operating-system-specific end-of-line combinations are not translated to the C '\n' character; this must be done by the client.
ctl_ms_read_char returns a non-negative character if the character was read without error, otherwise otherwise an error code. Specifically, reading beyond the end of file returns the error CTL_MS_READ_PAST_EOF_ERROR.
ctl_ms_read_char is thread-safe.