skeleton, as %location use is not cleaned up yet.
* src/scan-gram.l (handle_dollar, handle_destructor_at)
(handle_action_at): New.
(handle_at, handle_action_dollar, handle_destructor_dollar): Take
a braced_code_t and a location as additional arguments.
(handle_destructor_dollar): Instead of requiring `b4_eval', just
unquote one when outputting `b4_dollar_dollar'.
Adjust callers.
* data/bison.simple (b4_eval): Remove.
(b4_symbol_destructor): Adjust.
* tests/input.at (Invalid @n): Adjust.
* tests/output.at (AT_CHECK_OUTPUT): Likewise.
* tests/headers.at (AT_TEST_CPP_GUARD_H): Ditto.
* tests/semantic.at (Parsing Guards): Similarly.
* src/reader.at (readgram): Complain if the last rule is not ended
with a semi-colon.