Add ping probe support

Use liboping (new dependency) to add 'ping XXX' entries support in .cfg
file, where XXX can be either IP address or FQDN.

Sample output:
...
  ping
    ya.ru
      IP: 2a02:6b8::2:242
      dropped: 3/3
    8.8.8.8
      IP: 8.8.8.8
      dropped: 0/3
      latency: 20.4 ms
      TTL: 120
...

N. B: to gather actual ping statistic we have to be able to send ICMP
requests (have enough privileges to work with RAW sockets).

Related: SYS#2655
Change-Id: Ife32540b532fb54368f63c78fb7837b84d4e8c76
diff --git a/src/Makefile.am b/src/Makefile.am
index cb85da2..d0d6a22 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,11 +24,12 @@
 libintern_la_SOURCES = simple_ctrl.c
 libintern_la_LIBADD = $(LIBOSMOCORE_LIBS) $(LIBOSMOGSM_LIBS)
 
-osmo_sysmon_CFLAGS = $(LIBMNL_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(AM_CFLAGS)
+osmo_sysmon_CFLAGS = $(LIBMNL_CFLAGS) $(LIBOSMOVTY_CFLAGS) $(LIBOPING_CFLAGS) $(AM_CFLAGS)
 
 osmo_sysmon_LDADD = $(LDADD) \
 	$(LIBOSMOVTY_LIBS) \
 	$(LIBMNL_LIBS) \
+	$(LIBOPING_LIBS) \
 	$(NULL)
 
 osmo_sysmon_SOURCES = \
@@ -37,6 +38,7 @@
 	osysmon_sysinfo.c \
 	osysmon_rtnl.c \
 	osysmon_file.c \
+	osysmon_ping.c \
 	osysmon_main.c \
 	$(NULL)