%printer: support both yyo and yyoutput.

lalr1.cc used to support yyo, but not yyoutput.  Support both,
but document only yyoutput (at least until there is some consensus
on this).

* data/c.m4 (yy_symbol_value_print): Also support yyo.
* data/glr.cc  (yy_symbol_value_print_): Support both yyo and yyoutput.
* data/lalr1.cc: Also support yyoutput.
* doc/bison.texinfo: Explicitly use yyoutput in the examples.
* examples/mfcalc/mfcalc.test: Test the -p option.
(cherry picked from commit c50263271d)

Conflicts:

	data/c.m4
	data/lalr1.cc
	doc/bison.texinfo
	etc/Makefile.am

data/c.m4

@@ -456,6 +456,8 @@ m4_define_default([b4_yy_symbol_print_generate],
 b4_locations_if([, [[YYLTYPE const * const yylocationp], [yylocationp]]])[]dnl
 m4_ifset([b4_parse_param], [, b4_parse_param]))[
 {
+  FILE *yyo = yyoutput;
+  YYUSE (yyo);
   if (!yyvaluep)
     return;
 ]b4_locations_if([  YYUSE (yylocationp);

data/glr.cc

@@ -151,9 +151,11 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
   ]b4_parser_class_name[::yy_symbol_value_print_ (int yytype,
 			   const semantic_type* yyvaluep, const location_type* yylocationp)
   {
-    /* Pacify ``unused variable'' warnings.  */
-    YYUSE (yyvaluep);
     YYUSE (yylocationp);
+    YYUSE (yyvaluep);
+    std::ostream& yyoutput = debug_stream ();
+    std::ostream& yyo = yyoutput;
+    YYUSE (yyo);
     switch (yytype)
       {
   ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))dnl

data/lalr1.cc

@@ -446,6 +446,9 @@ do {					\
   {
     YYUSE (yylocationp);
     YYUSE (yyvaluep);
+    std::ostream& yyo = debug_stream ();
+    std::ostream& yyoutput = yyo;
+    YYUSE (yyoutput);
     switch (yytype)
       {
   ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))dnl