Base of enhanced ICMP support

Translated ICMPv4 packets are statically allocated
ICMPv4 sanitizes size of payload
Fix of an overflow
Generalised translation of ICMPv4 error packets
Completed translating of ICMPv4 errors
Completed enhanced ICMP support
Better way to filter out IPv4 flags
Automatic disabling of segmentation offload
Dropped compiling of DNS64 proxy
Updated README, ChangeLog and AUTHORS
Written NEWS and bumped version to 0.2.0