Remove lots of $Header's and a few $Id's that all belong to the former
CVS repository of tcpdump itself. These keywords have been frozen since
the migration to git in late 2008.
the top-level directory, remove from them all stuff not needed by
tcpdump, include them rather than the system's header files, and get rid
of assorted unnecessary include files.
This means you don't need to check for "slip.h" when building
"print-sl.c", stubbing it out on systems that don't have "slip.h". We
also don't need to build the stuff in "print-vjc.c" only on BSD/OS.
Use "u_int32_t" and "u_int16_t" rather than "u_int" and "u_short" for
structure members in "print-chdlc.c".
Move PPP_HDRLEN from "print-ppp.c" to "ppp.h", as per the XXX comment in
"print-ppp.c".
