[PATCH] maint: remove obsolete AC_HEADER_STDC macro

Avoid the following warning:
  configure.ac:208: warning: The macro `AC_HEADER_STDC' is obsolete.

* configure.ac (AC_HEADER_STDC): Remove, and ...
(AC_CHECK_INCLUDES_DEFAULT): ... add this instead.
---
 configure.ac | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index d6341f17..019a2557 100644
--- a/configure.ac
+++ b/configure.ac
@@ -205,7 +205,8 @@ AC_CHECK_LIB([m],[fabs],[FINDLIBS="-lm $FINDLIBS"]
 AC_SUBST([FINDLIBS])
 
 dnl Checks for header files.
-AC_HEADER_STDC
+AC_CHECK_INCLUDES_DEFAULT
+
 AC_CHECK_HEADERS(sys/param.h mntent.h sys/mnttab.h sys/mntio.h sys/mkdev.h)
 dnl fdleak.c needs sys/resource.h because it calls getrlimit(2).
 AC_CHECK_FUNCS(getrlimit)
-- 
2.36.0