For push mode, convert yyparse from a macro to a function, invoke yylex

instead of passing a yylexp argument to yypull_parse, and don't
generate yypull_parse or yyparse unless %push-pull-parser is declared.
Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2006-12/msg00163.html>.
* data/bison.m4 (b4_pull_if): New.
* data/c.m4 (b4_identification): Define YYPULL similar to YYPUSH.
* data/push.c: Improve M4 quoting a little.
(b4_generate_macro_args, b4_parenthesize): Remove.
(yyparse): If there's a b4_prefix, #define this to b4_prefix[parse]
any time a pull parser is requested.
Don't #define this as a wrapper around yypull_parse.  Instead, when
both push and pull are requested, make it a function that does that
same thing.
(yypull_parse): If there's a b4_prefix, #define this to
b4_prefix[pull_parse] when both push and pull are requested.
Don't define this as a function unless both push and pull are
requested.
Remove the yylexp argument and hard-code yylex invocation instead.
* etc/bench.pl.in (bench_grammar): Use %push-pull-parser instead of
%push-parser.
* src/getargs.c (pull_parser): New global initialized to true.
* getargs.h (pull_parser): extern it.
* src/output.c (prepare): Insert pull_flag muscle.
* src/parse-gram.y (PERCENT_PUSH_PULL_PARSER): New token.
(prologue_declaration): Set both push_parser and pull_parser = true for
%push-pull-parser.  Set push_parser = true and pull_parser = false for
%push-parser.
* src/scan-gram.l: Don't accept %push_parser as an alternative to
%push-parser since there's no backward-compatibility concern here.
Scan %push-pull-parser.
* tests/calc.at (Simple LALR(1) Calculator): Use %push-pull-parser
instead of %push-parser.
* tests/headers.at (export YYLTYPE): Make yylex static, and don't
prototype it in the module that calls yyparse.
* tests/input.at (Torturing the Scanner): Likewise.
* tests/local.at (AT_PUSH_IF): Check for %push-pull-parser as well.

src/parse-gram.y

@@ -156,6 +156,8 @@ static int current_prec = 0;
   PERCENT_PROVIDES        "%provides"
   PERCENT_PURE_PARSER     "%pure-parser"
   PERCENT_PUSH_PARSER     "%push-parser"
+  PERCENT_PUSH_PULL_PARSER
+                          "%push-pull-parser"
   PERCENT_REQUIRE	  "%require"
   PERCENT_REQUIRES        "%requires"
   PERCENT_SKELETON        "%skeleton"
@@ -257,7 +259,8 @@ 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; pull_parser = false; }
+| "%push-pull-parser"           { push_parser = true; pull_parser = true; }
 | "%require" STRING             { version_check (&@2, $2); }
 | "%skeleton" STRING            { skeleton_arg ($2, 1, &@1); }
 | "%token-table"                { token_table_flag = true; }