Fix the "|" and "&" operators of the "byte" primitive.

Fix the "|" and "&" operators of the "byte" primitive.

In gen_byteop() the "=", "<" and ">" cases load the required packet byte
into the A register implicitly via gen_load_a(), but the other two cases
need to do it explicitly, otherwise A will hold the previous value and
the ALU instruction will take that as the input.

The bug was introduced in the tcpdump 2.0 release (January 1991, before
libpcap 0.0), which replaced filter.c with gencode.c.