[gparted] Enable C++11 compilation when using libsigc++ 2.5.1 and later (#758545)

[Curtis Gedak <gedakc src gnome org>]

commit 707bae6fed6783e84600c6143f0f4bfd7989f56f
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Thu Mar 24 16:09:43 2016 +0000

    Enable C++11 compilation when using libsigc++ 2.5.1 and later (#758545)
    
    As with glibmm [1] the latest versions of libsigc++ also uses ISO C++
    2011 features.  The NEWS file [2] says:
    
        2.5.1 (unstable):
    
        * Use (and require) C++11
          (Kjell Ahlstedt)
        * Using C++11 lambda functions to create sigc::slots:
          Avoid the need for SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE.
          (Kjell Ahlstedt)
    
    Without enabling C++11 compiler features, compilation of GParted with
    libsigc++ 2.5.1 and later fails with errors such as theses:
    
        /usr/include/sigc++-2.0/sigc++/trackable.h:40:3: warning: identifier 'noexcept' is a keyword in C++11 
[-Wc++0x-compat]
           trackable_callback(void* data, func_destroy_notify func) noexcept
           ^
    
    [1] d6d7cb2bbf2fc381b890f63bbbf626eacfc8cdf8
        Enable C++11 compilation when using glibmm 2.45.40 and later (#756035)
    
    [2] libsigc++ 2.5.1 NEWS file
        https://git.gnome.org/browse/libsigcplusplus/tree/NEWS?h=2.5.1
    
    Bug 758545 - gparted-0.24.0 fails to build with gnome 3.18 mm packages
                 (on Gentoo)

 configure.ac |   21 ++++++++++++++++++---
 1 files changed, 18 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 414b1cf..df19abb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -259,15 +259,30 @@ PKG_CHECK_EXISTS(
 )
 
 
-dnl Check for glibmm >= 2.45.40 and if found enable required C++11 compilation.
+need_cxx_compile_stdcxx_11=no
+dnl Check for glibmm >= 2.45.40 which requires 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()
+       [need_cxx_compile_stdcxx_11=yes
+        AC_MSG_RESULT([yes])
+       ],
+       [AC_MSG_RESULT([no])]
+)
+dnl Check for libsigc++ >= 2.5.1 which requires C++11 compilation.
+AC_MSG_CHECKING([for libsigc++ >= 2.5.1 which requires C++11 compilation])
+PKG_CHECK_EXISTS(
+       [sigc++-2.0 >= 2.5.1],
+       [need_cxx_compile_stdcxx_11=yes
+        AC_MSG_RESULT([yes])
        ],
        [AC_MSG_RESULT([no])]
 )
+dnl Enable C++11 compilation only if required.
+if test "x$need_cxx_compile_stdcxx_11" = xyes; then
+       AX_CXX_COMPILE_STDCXX_11()
+fi
+
 
 
 dnl======================