Inline pair production in json parser

Having this as a separate production has a noticeable performance
impact, and doesn't really make things clearer either.

Author: nikic

ext/json/json_parser.y

@@ -47,10 +47,6 @@ int json_yydebug = 1;
 
 %union {
 	zval value;
-	struct {
-		zend_string *key;
-		zval val;
-	} pair;
 }
 
 
@@ -66,10 +62,8 @@ int json_yydebug = 1;
 
 %type <value> start object key value array
 %type <value> members member elements element
-%type <pair> pair
 
 %destructor { zval_ptr_dtor_nogc(&$$); } <value>
-%destructor { zend_string_release_ex($$.key, 0); zval_ptr_dtor_nogc(&$$.val); } <pair>
 
 %code {
 static int php_json_yylex(union YYSTYPE *value, php_json_parser *parser);
@@ -130,30 +124,22 @@ members:
 ;
 
 member:
-		pair
+		key ':' value
 			{
 				parser->methods.object_create(parser, &$$);
-				if (parser->methods.object_update(parser, &$$, $1.key, &$1.val) == FAILURE) {
+				if (parser->methods.object_update(parser, &$$, Z_STR($1), &$3) == FAILURE) {
 					YYERROR;
 				}
 			}
-	|	member ',' pair
+	|	member ',' key ':' value
 			{
-				if (parser->methods.object_update(parser, &$1, $3.key, &$3.val) == FAILURE) {
+				if (parser->methods.object_update(parser, &$1, Z_STR($3), &$5) == FAILURE) {
 					YYERROR;
 				}
 				ZVAL_COPY_VALUE(&$$, &$1);
 			}
 ;
 
-pair:
-		key ':' value
-			{
-				$$.key = Z_STR($1);
-				ZVAL_COPY_VALUE(&$$.val, &$3);
-			}
-;
-
 array:
 		'['
 			{