Include <stdio.h> for the printf function.  This avoids an implicit
function declaration in this configure check, causing to fail
unconditionally with compilers that do not support them.

Submitted upstream: <https://github.com/steve-o/openpgm/pull/73>

diff -ur openpgm-release-5-2-122.orig/openpgm/pgm/configure.ac openpgm-release-5-2-122/openpgm/pgm/configure.ac
--- openpgm-release-5-2-122.orig/openpgm/pgm/configure.ac	2012-12-04 03:56:54.000000000 +0100
+++ openpgm-release-5-2-122/openpgm/pgm/configure.ac	2023-01-03 16:07:39.751560631 +0100
@@ -207,7 +207,7 @@
 # sprintf, caveat http://savannah.gnu.org/patch/?6848 (ax_c_printf_thsep)
 AC_MSG_CHECKING([for printf thousands' grouping])
 AC_COMPILE_IFELSE(
-	[AC_LANG_PROGRAM(,[[printf ("%'d", 1000000);]])],
+	[AC_LANG_PROGRAM([[#include <stdio.h>]],[[printf ("%'d", 1000000);]])],
 	[AC_MSG_RESULT([yes])
 		CFLAGS="$CFLAGS -DHAVE_SPRINTF_GROUPING"],
 	[AC_MSG_RESULT([no])])