[gparted] Enable C++11 compilation when using glibmm 2.45.40 and later (#756035)

[Curtis Gedak <gedakc src gnome org>]

commit d6d7cb2bbf2fc381b890f63bbbf626eacfc8cdf8
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sun Oct 4 11:26:51 2015 +0100

    Enable C++11 compilation when using glibmm 2.45.40 and later (#756035)
    
    Glibmm 2.45.40 and later uses features in the ISO C++ 2011 standard.
    The NEWS file [1] says:
    
        Changes in 2.46 compared to 2.44:
    
        General:
        * Use, and require C++11, using features such as move operations,
          noexcept auto, = delete, nulltpr, override.
          (Murray Cumming, Kjell Ahlstedt)
    
    Also found this by Murray Cumming [2]:
    
        glibmm 2.45.40 requires C++11, both for its own build and by any
        apps that use it.  gtkmm also now requires C++11.
    
        I think you are seeing a symptom of building the application without
        C++11 support.  For instance, using CXXFLAGS="--std=c++11", though
        you'd be better of using an m4 macro such as
        AX_CXX_COMPILE_STDCXX_11().
    
    Without enabling C++11 compiler features, compilation of GParted with
    the latest glibmm library fails with errors such as these:
    
        /usr/include/glibmm-2.4/glibmm/ustring.h:267:14: error: expected ';' at end of member declaration
           ~ustring() noexcept;
                    ^
        /usr/include/glibmm-2.4/glibmm/ustring.h:267:14: error: 'noexcept' does not name a type
           ~ustring() noexcept;
                      ^
        /usr/include/glibmm-2.4/glibmm/ustring.h:267:14: note: C++11 'noexcept' only available with 
-std=c++11 or -std=gnu++11
    
    [1] glibmm NEWS file
        https://git.gnome.org/browse/glibmm/tree/NEWS?id=934e8290ce913b12e251ea617d0fc8ac53c385c6
    
    [2] https://bugs.launchpad.net/ubuntu/+source/glibmm2.4/+bug/1478367
    
    Bug 756035 - GParted does not compile with newer gtkmm libraries in
                 Fedora 23

 configure.ac |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index bc3a450..a11bd41 100644
--- a/configure.ac
+++ b/configure.ac
@@ -272,6 +272,17 @@ PKG_CHECK_EXISTS(
 )
 
 
+dnl Check for glibmm >= 2.45.40 and if found enable required C++11 compilation.
+AC_MSG_CHECKING([for glibmm >= 2.45.40 which requires C++11 compilation])
+PKG_CHECK_EXISTS(
+       [glibmm-2.4 >= 2.45.40],
+       [AC_MSG_RESULT([yes])
+        AX_CXX_COMPILE_STDCXX_11()
+       ],
+       [AC_MSG_RESULT([no])]
+)
+
+
 dnl======================
 dnl check whether to build documentation - gnome-doc-utils
 dnl======================