[network] Make use of T3113 for paging

Add it to the configuration files and make use
of it in the the paging.c.
diff --git a/openbsc/src/openbsc.cfg.1-1 b/openbsc/src/openbsc.cfg.1-1
index bad6df7..d312843 100644
--- a/openbsc/src/openbsc.cfg.1-1
+++ b/openbsc/src/openbsc.cfg.1-1
@@ -12,6 +12,7 @@
  short name OpenBSC
  long name OpenBSC
  timer t3101 10
+ timer t3113 60
  bts 0
   type bs11
   band GSM900