Add a URL for Gnutella specs.

Add a URL for Gnutella specs.

Don't check, in the dissectors for particular Gnutella packets, whether
the packet goes past the end of the tvbuff - let that throw an exception
so unreassembled packets are shown as such.

Clean up indentation.

Boost GNUTELLA_MAX_SNAP_SIZE to 4096 (one Gnutella spec suggests that
packets should be < 4K), and use it to

	1) clamp the length of packets (so we don't do huge reassembly
	   or have problems when the total packet length, including the
	   header, overflows 32 bits)

and

	2) check the length of packets before using tcp_dissect_pdus(),
	   to distinguish between packets to be reassembled and a
	   transfer stream.

Pass the correct value to tcp_dissect_pdus() as the header length.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@13211 f5534014-38df-0310-8fa8-9805f1628bb7