Fix the test failure due to GCC warnings described in

Fix the test failure due to GCC warnings described in
<http://mail.gnu.org/pipermail/bug-bison/2002-November/001815.html>.
* data/glr.c (yyis_pact_ninf, yyis_table_ninf): New macros, which
evaluate to 0 if it's impossible for NINF to be in the respective
table.
(yygetLRActions, yyrecoverParseError): Use them.

* src/scan-gram.l (unexpected_end_of_file): Fix bug: columns were
counted in the token inserted at end of file.  Now takes
location_t *, not location_t, so that the location can be
adjusted.  All uses changed.

* tests/regression.at (Invalid inputs): Adjust wording in
diagnostic to match the new behavior.

* tests/torture.at (AT_DATA_TRIANGULAR_GRAMMAR,
AT_DATA_HORIZONTAL_GRAMMAR, AT_DATA_LOOKAHEADS_GRAMMAR,
AT_DATA_STACK_TORTURE): Replace `assert (x);' with `if (! (x))
abort ();'.  This reduces the runtime of the "Many lookaheads"
test from 27.6 to 2.7 minutes on a 440 MHz Ultrasparc III running
GCC 3.2.