Eliminate the parser_use_ast switch, which does nothing, and

exec_no_exec, which also does nothing in the new parser

parser.h

@@ -433,8 +433,4 @@ class parser_t
     void stack_trace(size_t block_idx, wcstring &buff) const;
 };
 
-/* Temporary */
-bool parser_use_ast(void);
-
-
 #endif