pimd: fix format strings

 * pim_igmp.c,
 * pim_igmpv3.c,
 * pim_pim.c,
 * pim_tlv.c: use %zu / %zd for size_t/ssize_t
 * pim_iface.c,
 * pim_ifchannel.c,
 * pim_mroute.c,
 * pim_neighbor.c,
 * pim_oil.c,
 * pim_ssmpingd.c,
 * pim_upstream.c: %zu for size_t
 * pim_cmd.c: %zu + a few (long long) casts for int64_t
 * pim_hello.c: %td for ptrdiff_t
pimd: use socklen_t consistently
pimd: fix worst char * <> uint8_t * intermingling
pimd: fix wtf code

 * pim_hello.c,
 * pim_neighbor.c: print pointers as %p
 * pim_time.c: comment out unused function
 * pim_zebra.c: wtf
Define pim_gettime() when PIM_GETTIME_USE_GETTIMEOFDAY is not available.
pimd: extend .gitignore
PIM_ZCLIENT_DEBUG enables zclient_socket() / zclient_socket_un() debug