Include <stdio.h> for the rename and perror functions.  This avoids an
implicit function declaration and build failures with future compilers.

Submitted upstream: <https://savannah.gnu.org/bugs/index.php?64036>

diff --git a/configure.ac b/configure.ac
index f80a6faf4889b285..170122ece4d3e92d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -384,6 +384,7 @@ m4_pushdef([GOOD],[test ! -f conftest-A && test -f conftest-B])dnl
 m4_pushdef([HMMM],[./conftest$EXEEXT && GOOD])dnl
   ZONK
 AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <stdio.h>
 #include <unistd.h>
 ]],[
   return 0 > rename ("conftest-A", "conftest-B");
@@ -480,6 +481,7 @@ AC_DEFINE_UNQUOTED([MMAP_SIGNAL],[${rcs_cv_mmap_signal-0}],
 
 AC_CACHE_CHECK([if `wait' can handle ignored SIGCHLD],[rcs_cv_tolerant_wait],[
 AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <stdio.h>
 #include <sys/types.h>
 #include <errno.h>
 #include <signal.h>