Don't apply the default %destructor or %printer to the error token,

Don't apply the default %destructor or %printer to the error token,
$undefined, or $accept.  This change fits the general rule that the
default %destructor and %printer are only for user-declared symbols,
and it solves several difficulties that are described in the new test
cases listed below.
* src/symtab.c (symbol_destructor_get, symbol_printer_get): Implement.
* tests/actions.at (Default %printer and %destructor are not for error
or $undefined, Default %printer and %destructor are not for $accept):
New test cases.