The number of bytes of tagged parameters should be computed by seeing

The number of bytes of tagged parameters should be computed by seeing
how many bytes remain in the packet starting at the initial offset of
the tagged parameters, not by seeing how many bytes remain in the packet
starting 4 bytes later.  (If you're trying to avoid counting a CRC that
appears at the end of the packet data, then you need to be sure there
*is* a CRC first; this may require using a different DLT_ type, in
libpcap, for those captures.)

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@4769 f5534014-38df-0310-8fa8-9805f1628bb7