Wrong byte order in the sequence number of ICMP echo requests (Little Endian)

[kontaxis]

In sendicmp.c the sequence number header field of ICMP echo requests is set to _icmp_seq which is a counter. However in little-endian architectures (x86) we need to change the byte order to big-endian so that it meets the network order convention. We can use htons(_icmp_seq) for this.