Do a bunch more length checking.

Make sure we don't run past the end of the packet or, when processing
the packet header, run past the end of the header.
don't include addrtoname.h needlessly
CARP: NDOize
NFS: unify TCP and UDP decoding, fix a bug

Change the UDP NFS printing format to match the current format of TCP
NFS printing (this complements commits f3051bc and 29d83db).

Update the man page to use the new format (this complements commit
2c86c75).

Restore printing of NFS packet length, which was broken in commit
68fe98a.
base struct tok on unsigned rather than signed int

This resolves a few Solaris-specific warnings emitted by
/opt/solarisstudio12.3/bin/cc like below:

warning: initializer does not fit or is out of range: 0xffffffff

(also happened for 0x80000000)
refine the previous change

This time eliminate a few instances of the code initializing struct tok
with negative values and squelch the warnings like below:

warning: initializer will be sign-extended: -1
dismiss decode_prefix.h

The only purpose of that header file was to provide two declarations
that now fit interface.h same well.
request more warnings during a Travis build
revert the latest change

./configure fails during the "BUILD_LIBPCAP=true BUILD_IPV6=true"
scenarios (both GCC and Clang):

Makefile:8411: warning: overriding commands for target `configure'
Makefile:455: warning: ignoring old commands for target `configure'
Makefile:8416: warning: overriding commands for target `stamp-h.in'
Makefile:460: warning: ignoring old commands for target `stamp-h.in'
Makefile:8421: warning: overriding commands for target `stamp-h'
Makefile:465: warning: ignoring old commands for target `stamp-h'
Makefile:8424: warning: overriding commands for target `Makefile'
Makefile:468: warning: ignoring old commands for target `Makefile'
Makefile:8427: warning: overriding commands for target `config.status'
Makefile:471: warning: ignoring old commands for target `config.status'
[...]
./config.status: line 1103: syntax error near unexpected token `done'
./config.status: line 1103: `done # for ac_tag'

I don't have the expertise to resolve it well right now, keep Travis CI
working meanwihle.
NDOize AH, BEEP and DTP decoders

Also remove some unnecessary passages.
Ask for more warnings during a Travis CI build 

.travis.yml: add 'touch .devel configure'
Travis script: refactor env section
don't include pcap.h needlessly

Both interface.h and netdissect.h include <pcap.h>, thus most files
should not include it regardless if these need it or not. The only
exceptions so far remain:
* addrtoname.c
* missing/datalinks.c
* missing/dlnames.c
* tcpdump.c
NDOize CIP, IPComp and IPFC decoders

Also remove some unneeded includes while at it.
Travis script: set silent operation for make

This change allows to see better the possible warnings
update Gisle's e-mail address per his request
remove unused print-netbios.c

The file had no purpose as the draft code in it wasn't compiled.
NDOize HSRP, IGRP and UDLD decoders
issues/286: get rid of Useless "no IPv4 address assigned" warning
Print some PPP CCP options; taken from issue #214, with changes.

Report the CCP protocol type as CCP.

Decode options for BSD, MRVCA, and DEFLATE compression.

Add some explanatory comments, and add some length checks, while we're
at it.