use -std=gnu++0x rather than -std=c++0x

The gcc default for C++ is -std=gnu++98, and -std=c++98 is used
explicitly or with -ansi, so the C++0x "default" should be gnu++0x.

configure.in

@@ -4333,9 +4333,9 @@ if test "$GCC" = "yes"; then
         AC_MSG_RESULT([no])
     fi
 
-    AC_MSG_CHECKING([whether $CC supports -std=c++0x without Language Defect 757])
+    AC_MSG_CHECKING([whether $CC supports -std=gnu++0x without Language Defect 757])
     save_CXXFLAGS=$CXXFLAGS
-    CXXFLAGS="$CXXFLAGS -std=c++0x"
+    CXXFLAGS="$CXXFLAGS -std=gnu++0x"
     AC_LANG_PUSH([C++])
 
     AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
@@ -6702,7 +6702,7 @@ if test "$with_system_mdds" = "yes"; then
     dnl ===================================================================
     AC_MSG_CHECKING([which hash container mdds shall use])
     if test "x$HAVE_CXX0X" = "xTRUE"; then
-        MDDS_CPPFLAGS="-std=c++0x"
+        MDDS_CPPFLAGS="-std=gnu++0x"
         AC_MSG_RESULT([std::unordered_map])
     else
         MDDS_CPPFLAGS="-DMDDS_HASH_CONTAINER_BOOST"

solenv/gbuild/platform/WNT_INTEL_GCC.mk

@@ -75,7 +75,7 @@ endif
 
 ifeq ($(HAVE_CXX0X),TRUE)
 # We can turn on additional useful checks with c++0x
-# FIXME still does not compile fully gb_CXXFLAGS += -std=c++0x
+# FIXME still does not compile fully gb_CXXFLAGS += -std=gnu++0x
 endif
 
 gb_LinkTarget_EXCEPTIONFLAGS += \

solenv/gbuild/platform/unxgcc.mk

@@ -103,7 +103,7 @@ endif
 ifeq ($(HAVE_CXX0X),TRUE)
 #Currently, as well as for its own merits, c++11/c++0x mode allows use to use
 #a template for SAL_N_ELEMENTS to detect at compiler time its misuse
-gb_CXXFLAGS += -std=c++0x
+gb_CXXFLAGS += -std=gnu++0x
 
 #We have so many std::auto_ptr uses that we need to be able to disable
 #warnings for those so that -Werror continues to be useful, seeing as moving