wiretap: ascend: Destroy lexer state after parsing

Lexer private structure is initialized but never destroyed or reused.

Change-Id: I61d43b4cb14a2d3b3706267eb393e4562adb00f9
Reviewed-on: https://code.wireshark.org/review/33809
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Tested-by: Petri Dish Buildbot
Reviewed-by: Guy Harris <guy@alum.mit.edu>

wiretap/ascend.y

@@ -485,6 +485,8 @@ run_ascend_parser(FILE_T fh, wtap_rec *rec, guint8 *pd,
   parser_state->pseudo_header->call_num[0] = '\0';
 
   status = yyparse(scanner, parser_state, fh);
+  ascendlex_destroy(&scanner);
+
   *err = parser_state->err;
   *err_info = parser_state->err_info;
   return status;