Fix short functions.

Author: Crell

Zend/tests/short_functions/short-func.phpt

@@ -1,10 +1,12 @@
 --TEST--
-
+Basic short functions return values.
 --FILE--
 <?php
 
 function test(int $a) => $a + 1;
 
+function test2(int $b) => return $b . 'error';
+
 print test(5);
 
 ?>

Zend/zend_language_parser.y

@@ -549,7 +549,7 @@ function_declaration_statement:
 		{ $$ = zend_ast_create_decl(ZEND_AST_FUNC_DECL, $2 | $13, $1, $4,
 		      zend_ast_get_str($3), $6, NULL, $11, $8, NULL); CG(extra_fn_flags) = $9; }
    | function returns_ref T_STRING backup_doc_comment '(' parameter_list ')' return_type
-     	backup_fn_flags '=>' inner_statement backup_fn_flags
+     	backup_fn_flags T_DOUBLE_ARROW inner_statement backup_fn_flags
      		{ $$ = zend_ast_create_decl(ZEND_AST_FUNC_DECL, $2, $1, $4,
      		      zend_ast_get_str($3), $6, NULL, zend_ast_create(ZEND_AST_RETURN, $11), $8, NULL); CG(extra_fn_flags) = $9; }
 ;