tests: add missing includes

* tests/actions.at, tests/c++.at, tests/headers.at,
* tests/regression.at: here.

tests/actions.at

@@ -425,6 +425,7 @@ AT_DATA_GRAMMAR([[input.y]],
 ]$3[
 %code
 {
+#include <stdio.h> /* putchar. */
 ]AT_YYERROR_DECLARE[
 ]AT_YYLEX_DECLARE[
 }
@@ -1728,6 +1729,7 @@ AT_DATA_GRAMMAR([[input.y]],
 # define YYSTYPE sem_type
 
 ]AT_CXX_IF([[
+# include <cstdio> // EOF.
 # include <iostream>
   namespace
   {

tests/c++.at

@@ -988,7 +988,8 @@ yy::parser::error (const std::string &m)
 
 # Another file to check syntax_error's linkage.
 AT_DATA_SOURCE([scan.cc],
-[[#include "input.hh"
+[[#include <cstdio>  // getchar
+#include "input.hh"
 
 // 'a': valid item, 's': syntax error, 'l': lexical error.
 int

tests/headers.at

@@ -127,6 +127,7 @@ AT_DATA_GRAMMAR([input.y],
 %define parse.error verbose
 ]AT_VARIANT_IF([%token <int> 'x'], [%union {int integer;}])[
 %code {
+#include <stdio.h> /* printf. */
 ]AT_PUSH_IF([[
 #if defined __GNUC__ && 7 == __GNUC__
 # pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
@@ -212,6 +213,7 @@ $2
   int integer;
 }
 %{
+#include <stdio.h> /* printf. */
 ]AT_PUSH_IF([[
 #if defined __GNUC__ && 7 == __GNUC__
 # pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

tests/regression.at

@@ -1309,6 +1309,7 @@ AT_BISON_OPTION_PUSHDEFS([%debug $1])
 
 AT_DATA_GRAMMAR([input.y],
 [[%code {
+#include <stdio.h> /* printf */
   ]AT_YYERROR_DECLARE[
   ]AT_YYLEX_DECLARE[
 }
@@ -1480,12 +1481,13 @@ AT_DATA_GRAMMAR([input.y],
 }
 
 %{
+#include <stdio.h> /* printf. */
   ]AT_YYERROR_DECLARE[
   ]AT_YYLEX_DECLARE[
 %}
 
 %%
-exp: 'a' { fprintf (stdout, "x: %d, y: %d\n", x, y); };
+exp: 'a' { printf ("x: %d, y: %d\n", x, y); };
 %%
 ]AT_YYERROR_DEFINE[
 ]AT_YYLEX_DEFINE(["a"])[