use do { } while (!bottom) instead of again: ... if (!bottom) goto again;

Teach tcpdump to recognize MPLS pseudowire with control words. Added
support to print encapsulated ethernet packets as well.

"Looks good" deraadt@

Print MPLS label as decimal and not hex. All other places we print MPLS
labels we use decimal.
OK jsg@ deraadt@

Add a best effort mpls decoder. From Jason L. Wright.
Since the encapsulated protocol information is not always
available in the MPLS tag stack. The decoder attempts
to guess the protocol.
ok brad@