increase libsmpp34 version requirement to 1.12

Only 1.12 contains some of the #defines that we're using with recent
commits.

Change-Id: I3743b10a1a5d2f1d42a61204273c1d00dc22b600
diff --git a/configure.ac b/configure.ac
index f184e78..871f7e5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -66,7 +66,7 @@
 AC_ARG_ENABLE([smpp], [AS_HELP_STRING([--enable-smpp], [Build the SMPP interface])],
     [osmo_ac_build_smpp="$enableval"],[osmo_ac_build_smpp="no"])
 if test "$osmo_ac_build_smpp" = "yes" ; then
-    PKG_CHECK_MODULES(LIBSMPP34, libsmpp34 >= 1.10)
+    PKG_CHECK_MODULES(LIBSMPP34, libsmpp34 >= 1.12)
     AC_DEFINE(BUILD_SMPP, 1, [Define if we want to build SMPP])
 fi
 AM_CONDITIONAL(BUILD_SMPP, test "x$osmo_ac_build_smpp" = "xyes")