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/configure.ac b/configure.ac
index 734ac99..d98de89 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,6 +43,8 @@
 PKG_CHECK_MODULES(LIBOSMOCTRL, libosmoctrl >= 0.11.0)
 PKG_CHECK_MODULES(LIBOSMOGSM, libosmogsm >= 0.11.0)
 PKG_CHECK_MODULES(LIBMNL, libmnl)
+dnl FIXME: bump to 1.10.0 once it's available on build slaves and remove workaround from osysmon_ping.c
+PKG_CHECK_MODULES(LIBOPING, liboping >= 1.9.0)
 
 dnl checks for header files
 AC_HEADER_STDC