Make %push-parser imply %pure-parser. This fixes several bugs; see

<http://lists.gnu.org/archive/html/bison-patches/2006-12/msg00148.html>.
* src/parse-gram.y (prologue_declaration): For %push-parser, also set
pure_parser = true.
* data/push.c: Don't bother testing b4_push_if when deciding whether
to expand b4_declare_parser_variables globally.
(yypush_parse): Likewise in here.

* data/push.c (yypush_parse): Add b4_parse_param to arguments.
(yy_reduce_print): Reformat M4 for readability.

src/parse-gram.c

@@ -2053,7 +2053,7 @@ yyreduce:
 
 /* Line 1269 of yacc.c  */
 #line 258 "parse-gram.y"
-    { push_parser = true; }
+    { push_parser = true; pure_parser = true; }
     break;
 
   case 29:

src/parse-gram.y

@@ -255,7 +255,7 @@ prologue_declaration:
 | "%output" "=" STRING          { spec_outfile = $3; }  /* deprecated */
 | "%parse-param" "{...}"	{ add_param ("parse_param", $2, @2); }
 | "%pure-parser"                { pure_parser = true; }
-| "%push-parser"                { push_parser = true; }
+| "%push-parser"                { push_parser = true; pure_parser = true; }
 | "%require" STRING             { version_check (&@2, $2); }
 | "%skeleton" STRING            { skeleton = $2; }
 | "%token-table"                { token_table_flag = true; }