* tests/regression.at (input.y): s/YYEOF/MYEOF/, as the skeleton

* tests/regression.at (input.y): s/YYEOF/MYEOF/, as the skeleton
defines it.
* data/glr.c (yystos): New.
(b4_yysymprint_generate, b4_yydestruct_generate): Invoke.
(YYDSYMPRINT): New.
(yyval): Don't define it, it is handled via M4.
(yyrecoverParseError): Free verbosely the discarded symbols.
* data/yacc.c (yysymprint): Remove, rather...
(b4_yysymprint_generate): invoke.
* data/c.m4 (b4_yysymprint_generate): New.
Accept pointers as arguments, as opposed to the version from
yacc.c.
(b4_yydestruct_generate): Likewise.
* tests/cations.at (Printers and Destructors): Use Bison directives
instead of CPP macros.
Don't rely on internal details.