No functional changes, but:

No functional changes, but:

Following Darren's suggestion, make Dijkstra happy and rewrite the
ipfw_chk() main loop removing a lot of goto's and using instead a
variable to store match status.

Add a lot of comments to explain what instructions are supposed to
do and how -- this should ease auditing of the code and make people
more confident with it.

In terms of code size: the entire file takes about 12700 bytes of text,
about 3K of which are for the main function, ipfw_chk(), and 2K (ouch!)
for ipfw_log().