TOOLS: Compile with c++11 by default if supported

This also adds an option to disable the use of c++11 and compile
with -ansi instead as we did before. But compilation of GUI tools
with a recent version of g++ will break when using -ansi.

configure

@@ -85,6 +85,7 @@ _debug_build=auto
 _release_build=auto
 _verbose_build=no
 _enable_prof=no
+_use_cxx11=yes
 # Default commands
 _ranlib=ranlib
 _strip=strip
@@ -335,6 +336,7 @@ Special configuration feature:
   --host=HOST             cross-compile to target HOST (arm-linux, ...)
 
 Optional Features:
+  --disable-c++11          disable building as C++11 when the compiler allows that
   --disable-debug          disable building with debugging symbols
   --enable-Werror          treat warnings as errors
   --enable-profiling       enable profiling
@@ -463,6 +465,12 @@ for ac_option in $@; do
 	--disable-debug)
 		_debug_build=no
 		;;
+	--enable-c++11)
+		_use_cxx11=yes
+		;;
+	--disable-c++11)
+		_use_cxx11=no
+		;;
 	--enable-Werror)
 		CXXFLAGS="$CXXFLAGS -Werror"
 		;;
@@ -875,34 +883,56 @@ else
 	echo found non-gcc compiler version ${cxx_version}
 fi
 
+#
+# Check whether the compiler supports C++11
+#
+have_cxx11=no
+cat > $TMPC << EOF
+int main(int argc, char *argv[]) { if (argv == nullptr) return -1; else return 0; }
+EOF
+cc_check -std=c++11 && have_cxx11=yes
+if test "$_use_cxx11" = "yes" ; then
+	_use_cxx11=$have_cxx11
+fi
+
 #
 # Setup compiler specific CXXFLAGS now that we know the compiler version.
 # Foremost, this means enabling various warnings.
 # In addition, we set CXX_UPDATE_DEP_FLAG for GCC >= 3.0 and for ICC.
 #
 if test "$have_gcc" = yes ; then
 	if test "$_cxx_major" -ge "3" ; then
-		case $_host_os in
-		# newlib-based system include files suppress non-C89 function
-		# declarations under __STRICT_ANSI__
-		amigaos* | android | dreamcast | ds | gamecube | mingw* | n64 | psp | ps2 | wii | wince )
-			;;
-		*)
-			CXXFLAGS="$CXXFLAGS -ansi"
-			;;
-		esac
+		# Try to use ANSI mode when C++11 is disabled.
+		if test "$_use_cxx11" = "no" ; then
+			case $_host_os in
+			# newlib-based system include files suppress non-C89 function
+			# declarations under __STRICT_ANSI__
+			amigaos* | android | dreamcast | ds | gamecube | mingw* | n64 | psp | ps2 | wii | wince )
+				;;
+			*)
+				CXXFLAGS="$CXXFLAGS -ansi"
+				;;
+			esac
+		fi
 		CXXFLAGS="$CXXFLAGS -W -Wno-unused-parameter"
 		add_line_to_config_mk 'HAVE_GCC3 = 1'
 		add_line_to_config_mk 'CXX_UPDATE_DEP_FLAG = -MMD -MF "$(*D)/$(DEPDIR)/$(*F).d" -MQ "$@" -MP'
-	fi;
+	fi
 
 	if test "$_cxx_major" -eq 4 && test "$_cxx_minor" -ge 3 || \
 	   test "$_cxx_major" -gt 4 ; then
 		CXXFLAGS="$CXXFLAGS -Wno-empty-body"
 	else
 		CXXFLAGS="$CXXFLAGS -Wconversion"
-	fi;
-fi;
+	fi
+fi
+
+echo_n "Building as C++11... "
+if test "$_use_cxx11" = "yes" ; then
+	CXXFLAGS="$CXXFLAGS -std=c++11"
+fi
+echo $_use_cxx11
+
 
 # By default, we add -pedantic to the CXXFLAGS to catch some potentially
 # non-portable constructs, like use of GNU extensions.