Add a sanity check on packet header length

Add a sanity check on packet header length

The packet length must be <= MAXIMUM_SNAPLEN.

Currently, there is no D-Bus printer, thus no need for a bigger length.

Now a pachet is valid if:
capture length != 0,
packet length != 0,
capture length <= MAXIMUM_SNAPLEN,
packet length <= MAXIMUM_SNAPLEN,
packet length >= capture length.

Moreover:
Fix the packet header lengths of some fuzzed pcap files:
If the lengths are > MAXIMUM_SNAPLEN, set them to MAXIMUM_SNAPLEN.
Thus they will be always usable with this new sanity check.