uipc: Remove never used last pr entry of localdomain
incsum: Const-fy mbuf parameter
icmp: Utilize in_cksum_skip()

This avoids unnecessary m_data and m_len adjustment before and after
in_cksum().
libkern: Add inet_ntop()

Taken-from: FreeBSD r213103
build: Add ICMPPRINTFS as global option