Fix stupid mistake in grammar

Author: rswinkle

README.md

@@ -70,7 +70,7 @@ It also of course supports actually using the macros.
 translation_unit -> top_level_declaration
  translation_unit top_level_declaration
 
-declaration_list  -> declaration
+top_level_declaration -> declaration
  function_definition
 
 function_definition -> declaration_specifier function_declarator compound_statement