parsergen: revert the allowance for "non-critical" conflicts.

Having improved the parsing approach, I don't get any
"non-critical" conflicts any more, and I no longer think
they aren't critical.

Conflicts can often be resolved with precendence if they cannot
be resolved any other way.

So treat all conflict, except shift/reduce on NEWLINE, as genuine
conflicts.

Signed-off-by: NeilBrown <neil@brown.name>