Currently, CodeQL mis-identifies a couple instances of the
usually-legitimate "User-controlled data may not be null terminated"
problem.

In these instances, CodeQL thinks that `packet_txt_read()` fails to
NUL-terminate (not actually "null"... tsk, tsk) the string. But it
totally does! Here is the current definition of that function:

	size_t packet_txt_read(char *buf, size_t count, FILE *stream)
	{
		size_t len;

		len = packet_bin_read(buf, count, stream);
		if (len && buf[len - 1] == '\n')
		{
			len--;
		}

		buf[len] = 0;
		return len;
	}

The `buf[len] = 0` statement guarantees that the string is
NUL-terminated.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>