Import new gnulib.

m4/strchrnul.m4

@@ -1,5 +1,5 @@
-# strchrnul.m4 serial 7
-dnl Copyright (C) 2003, 2007, 2009, 2010 Free Software Foundation, Inc.
+# strchrnul.m4 serial 9
+dnl Copyright (C) 2003, 2007, 2009-2013 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -10,10 +10,39 @@ AC_DEFUN([gl_FUNC_STRCHRNUL],
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  AC_REPLACE_FUNCS([strchrnul])
+  AC_CHECK_FUNCS([strchrnul])
   if test $ac_cv_func_strchrnul = no; then
     HAVE_STRCHRNUL=0
-    gl_PREREQ_STRCHRNUL
+  else
+    AC_CACHE_CHECK([whether strchrnul works],
+      [gl_cv_func_strchrnul_works],
+      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <string.h> /* for strchrnul */
+]], [[const char *buf = "a";
+      return strchrnul (buf, 'b') != buf + 1;
+    ]])],
+        [gl_cv_func_strchrnul_works=yes],
+        [gl_cv_func_strchrnul_works=no],
+        [dnl Cygwin 1.7.9 introduced strchrnul, but it was broken until 1.7.10
+         AC_EGREP_CPP([Lucky user],
+           [
+#if defined __CYGWIN__
+ #include <cygwin/version.h>
+ #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 9)
+  Lucky user
+ #endif
+#else
+  Lucky user
+#endif
+           ],
+           [gl_cv_func_strchrnul_works="guessing yes"],
+           [gl_cv_func_strchrnul_works="guessing no"])
+        ])
+      ])
+    case "$gl_cv_func_strchrnul_works" in
+      *yes) ;;
+      *) REPLACE_STRCHRNUL=1 ;;
+    esac
   fi
 ])