* src/main.c (main): If there are complains after grammar

* src/main.c (main): If there are complains after grammar
reductions, then output the report anyway if requested, then die.
* src/symtab.c (bucket_new): Initialize `value' to -1, not 0.
* src/reader.c (eoftoken): New.
(parse_token_decl): If the token being defined has value `0', it
is the eoftoken.
(packsymbols): No longer hack `tags' to insert `$' by hand.
Be sure to preserve the value of the eoftoken.
(reader): Make sure eoftoken is defined.
Initialize nsyms to 0: now eoftoken is created just like the others.
* src/print.c (print_grammar): Don't special case the eof token.
* src/regression.at: Adjust: `$' has value 0, not -1, which was a
lie anyway, albeit pleasant.
* tests/calc.at: Exercise error messages with eoftoken.
Change the grammar so that empty input is invalid.
Adjust expectations.
When yyungeting, be sure to use a valid yylloc: use last_yylloc.