Update etc/inc/interfaces.inc

With the new support for multiple stf interfaces their names have changed. Adapt the regex pattern.
Do more strict checks. Also silence some more log_error under debug. Also do some sanity checks on rc.newwanipv6 before doing any operation
Merge pull request #362 from bcyrill/patch-4

Adapt regex pattern for new stp interface naming
Fix whitespaces and indent
Fix indent
is_ipaddr_configured() now returns VIPS
Avoid mpd based services to set localip to an already used IP on the system. It should fix #1723
Syntax error in vpn_pppoe.php
Merge pull request #363 from phil-davis/master

Syntax error in vpn_pppoe.php
Fixes links and PPS

This change fixes:
- Interface value in the links to the "Firewall: Traffic Shaper" page;
- Read the proper PPS value from the qstats XML file. 
Do the right thing here
Actually destroy in this case
Create link_interface_to_track6 to make code more readble and easily trackble. Also improve the generation of rules to avoid creating problems during filter reload and some optimizations with it
Do not do any operation if its not necessary
Destroy the stf interface to avoid issues with ipv6 interface assignment. Also delete any previous address on track6 interfaces before assigning a new one.
Merge pull request #364 from mdima/master

Fix for links and PPS
Correct name as reported by phil-davis@github
Do delayed handling of track6 interfaces a bit earlier. More thoughts need to be done on the track6 configuration
Fix a typo
Add missing parameter to interface_track6_configure() call