Fix test failure reported by Tom Lane in

Fix test failure reported by Tom Lane in
<http://lists.gnu.org/archive/html/bug-bison/2006-10/msg00000.html>
and try to make such failures easier to catch in the future.
* data/glr.c (YYTRANSLATE): Don't check for nonpositive arg;
that's now the caller's responsibility.
(yyprocessOneStack, yyrecoverSyntaxError, yyparse):
Set yychar = YYEOF if it's negative.
* tests/actions.at (yylex): Abort if asked to read past EOF.
* tests/conflicts.at (yylex): Likewise.
* tests/cxx-type.at (yylex): Likewise.
* tests/glr-regression.at (yylex): Likewise.
* tests/input.at (yylex): Likewise.
* tests/regression.at (yylex): Likewise.
* tests/torture.at (yylex): Likewise.