Add feature: support ICMP type 13/14 timestamps

[gsnw-sebast]

This is a development branch. (Issues: #265)

The current version has no output yet, but can be tested with GDP. Please note that root rights are required for icmp type 13 queries

Build

./autogen.sh
./configure --enable-debug
make CFLAGS="-g -O0 -fprofile-arcs -ftest-coverage"

GDB Usage

gdb fping
set args --icmp-timestamp 127.0.0.1
break fping.c:2289

print *icp

[coveralls]

coverage: 86.772% (-0.8%) from 87.614%
when pulling b70a947 on gsnw:icmp-13_and_14-dev
into b32852c on schweikert:develop.

[gsnw-sebast]

The current update outputs the output directly with ./fping --icmp-timestamp 127.0.0.1

I'm still thinking about putting the ip header returns from decode_icmp_ipv4 into an extra structure. Because the many returns make it a bit overloaded

[gsnw-sebast]

Development is finished and therefore the pull-request is closed and a new one is created with the final version