For push mode, add pull wrappers around yypush_parse.

* data/push.c: (b4_generate_macro_args, b4_parenthesize): New macros.
(yypull_parse): New function wrapping yypush_parse.
(yyparse): New #define wrapping yypull_parse.
* tests/calc.at (_AT_DATA_CALC_Y): Call yyparse even when %push-parser
is declared.
* tests/headers.at (export YYLTYPE): Make yylex global.  For push mode,
prototype yylex in the module that calls yyparse, and don't prototype
yyparse there.  Otherwise, the yyparse expansion won't compile.
* tests/input.at (Torturing the Scanner): Likewise.

tests/headers.at

@@ -94,7 +94,9 @@ AT_DATA_GRAMMAR([input.y],
 #include <stdio.h>
 #include <stdlib.h>
 
-static int
+int my_lex (void);
+
+int
 my_lex (void)
 {
   return EOF;
@@ -118,7 +120,11 @@ AT_DATA([caller.c],
 [[#include "input.h"
 YYLTYPE *my_llocp = &my_lloc;
 
+#ifndef YYPUSH_DECLS
 int my_parse (void);
+#else
+int my_lex (void);
+#endif
 
 int
 main (void)