bpf-lua -O0 attempts to compare string with number

[kbara]

% ./env tools/pipe-lua-libpcap-match -O0 tests/data/wingolog.pcap '1 * 1 >= 1' 1       
luajit: /home/me/igalia/pflua/src/pf/bpf.lua:65: attempt to compare string with number
stack traceback:
    ~/igalia/pflua/src/pf/bpf.lua:65: in function 'runtime_u32'
    ~/igalia/pflua/src/pf/bpf.lua:98: in function 'is_power_of_2'
    ~/igalia/pflua/src/pf/bpf.lua:253: in function 'alu'
    ~/igalia/pflua/src/pf/bpf.lua:327: in function 'compile_lua'
    ~/igalia/pflua/src/pf/bpf.lua:444: in function 'compile_filter'
    ~/igalia/pflua/tools/pipe-lua-libpcap-match:39: in function 'main_filter'
    ~/igalia/pflua/tools/pipe-lua-libpcap-match:52: in main chunk
    [C]: at 0x00404bc0

Without optimization:
% ./env tools/pipe-lua-libpcap-match  tests/data/wingolog.pcap '1 * 1 >= 1' 1 
OK: pure-lua, bfp-lua, and libpcap pipelines matched: all true