Fix IPv6/IPX statistics generation

Use a doubly-linked list and iterate on the reversed statistics list to always test the bigger strings first

Bug: 10813
Change-Id: Ibfedac9648db58e6dadc2334eec678e26daca906
Reviewed-on: https://code.wireshark.org/review/6140
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>