Make the value argument to "gen_ncmp()" a bpf_int32, the same as the

Make the value argument to "gen_ncmp()" a bpf_int32, the same as the
value arguments are to other routines.  Do the same with the value
argument to "gen_atmfield_code()".

"gen_load_a()" can return more than one statement; append to the list of
statements it returns with "sappend()", rather than manually appending
to the first statement.

Fix the argument list to one "gen_ncmp()" call, and get rid of the casts
in the other calls, as the arguments already have the right types.

Fix the casts in calls to "gen_atmfield_code()".