Include <stdio.h> for printf in __FUNCTION__ check.  Otherwise, the
check will fail with compilers which do not implement implicit
function declarations (a C feature that was removed in 1999 from the
language), no matter if the compiler supports FUNCTION or not.

Submitted upstream: <https://github.com/dajobe/raptor/pull/56>

diff --git a/configure b/configure
index b0091892a210361d..08501ac8ed5e4fe1 100755
--- a/configure
+++ b/configure
@@ -13747,6 +13747,8 @@ esac
 $as_echo_n "checking whether __FUNCTION__ is available... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
+
+#include <stdio.h>
 int main() { printf(__FUNCTION__); }
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"; then :
diff --git a/configure.ac b/configure.ac
index 10ff870805b82e65..40a8548b6406866a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -312,7 +312,9 @@ AC_C_BIGENDIAN
 AC_C_INLINE
 
 AC_MSG_CHECKING(whether __FUNCTION__ is available)
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([int main() { printf(__FUNCTION__); }])],
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+#include <stdio.h>
+int main() { printf(__FUNCTION__); }])],
     [AC_DEFINE([HAVE___FUNCTION__], [1], [Is __FUNCTION__ available])
      AC_MSG_RESULT(yes)],
     [AC_MSG_RESULT(no)])