[glom] Use C++14.

[Murray Cumming <murrayc src gnome org>]

commit 72d7b241a1ee81be9b7c2f2bf19698906e32257d
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Feb 4 22:27:00 2016 +0100

    Use C++14.
    
    So we can use std::make_unique(), for instance.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index eddc3e6..c7fd225 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,7 +31,7 @@ AC_PROG_CC
 AM_PROG_CC_C_O
 AC_PROG_CXX
 
-AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory])
+AX_CXX_COMPILE_STDCXX([14], [noext], [mandatory])
 
 LT_PREREQ([2.2.0])
 LT_INIT([disable-static win32-dll])