[libgdamm] Require C++14 because newer glibmm does.

[Murray Cumming <murrayc src gnome org>]

commit 213bb8b9a9bdbe9a3b29fb368109f5c970cafeb6
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Nov 14 13:14:18 2016 +0100

    Require C++14 because newer glibmm does.

 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d93b6e2..9ecf78c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -24,7 +24,7 @@ AC_CONFIG_AUX_DIR([build])
 AC_CONFIG_MACRO_DIR([build])
 AC_CONFIG_HEADERS([build/config.h libgda/libgdammconfig.h])
 
-MM_PREREQ([0.9.8])
+MM_PREREQ([0.9.10])
 MM_INIT_MODULE([libgdamm-6.0])
 
 # Copy the mm-common .pl scripts into docs/,
@@ -40,7 +40,7 @@ AM_MAINTAINER_MODE
 AC_ARG_VAR([ACLOCAL_FLAGS], [aclocal flags, e.g. -I <macro dir>])
 
 AC_PROG_CXX
-MM_AX_CXX_COMPILE_STDCXX_11([noext],[mandatory])
+MM_AX_CXX_COMPILE_STDCXX([14],[noext],[mandatory])
 
 AC_DISABLE_STATIC
 AC_LIBTOOL_WIN32_DLL