Reassem: Reject blocks overflowing 64bit upper

The reassembler logic isn't wrap around safe, so just truncate or
reject such blocks. For files specifically, a byte offset in the
2**64 bytes represents 16EiB which is the maximum size supported
by BTRFS or NTFS (and probably nothing we'd ever see in practice).

src/analyzer/protocol/tcp/TCP_Reassembler.cc

@@ -371,6 +371,7 @@ void TCP_Reassembler::BlockInserted(DataBlockMap::const_iterator it)
 	{
 	const auto& start_block = it->second;
 
+	assert(start_block.seq < start_block.upper);
 	if ( start_block.seq > last_reassem_seq || start_block.upper <= last_reassem_seq )
 		return;