Port AC_CHECK_HEADER_STDBOOL to C++11

* lib/autoconf/headers.m4: Port to C++11.
Problem reported by David Seifert in:
http://lists.gnu.org/archive/html/bug-gnulib/2016-05/msg00052.html

diff --git a/lib/autoconf/headers.m4 b/lib/autoconf/headers.m4
index bb532e5169ddd2ca1c22fd543f8fce886c31aebe..0c44973b0c2b7e73b0cafbea7c2c0806faf0d1fb 100644 (file)
--- a/lib/autoconf/headers.m4
+++ b/lib/autoconf/headers.m4
@@ -529,21 +529,25 @@ AC_DEFUN([AC_CHECK_HEADER_STDBOOL],
         [AC_LANG_PROGRAM(
            [[
              #include <stdbool.h>
-             #ifndef bool
-              "error: bool is not defined"
-             #endif
-             #ifndef false
-              "error: false is not defined"
-             #endif
-             #if false
-              "error: false is not 0"
-             #endif
-             #ifndef true
-              "error: true is not defined"
-             #endif
-             #if true != 1
-              "error: true is not 1"
+
+             #if __cplusplus < 201103
+              #ifndef bool
+               "error: bool is not defined"
+              #endif
+              #ifndef false
+               "error: false is not defined"
+              #endif
+              #if false
+               "error: false is not 0"
+              #endif
+              #ifndef true
+               "error: true is not defined"
+              #endif
+              #if true != 1
+               "error: true is not 1"
+              #endif
              #endif
+
              #ifndef __bool_true_false_are_defined
               "error: __bool_true_false_are_defined is not defined"
              #endif