Correct a number of evolved problems with inp_vflag and inp_flags:

Correct a number of evolved problems with inp_vflag and inp_flags:
certain flags that should have been in inp_flags ended up in inp_vflag,
meaning that they were inconsistently locked, and in one case,
interpreted.  Move the following flags from inp_vflag to gaps in the
inp_flags space (and clean up the inp_flags constants to make gaps
more obvious to future takers):

  INP_TIMEWAIT
  INP_SOCKREF
  INP_ONESBCAST
  INP_DROPPED

Some aspects of this change have no effect on kernel ABI at all, as these
are UDP/TCP/IP-internal uses; however, netstat and sockstat detect
INP_TIMEWAIT when listing TCP sockets, so any MFC will need to take this
into account.

MFC after:      1 week (or after dependencies are MFC'd)
Reviewed by:    bz