This patch is to enable displaying arguments of tracepoint
probe in listing mode -L. The example output is like
$stap -L 'kernel.trace("block_bio*")'
kernel.trace("block_bio_bounce") $q:struct request_queue* $bio:struct bio*
kernel.trace("block_bio_backmerge") $q:struct request_queue* $bio:struct bio*
kernel.trace("block_bio_complete") $q:struct request_queue* $bio:struct bio*
kernel.trace("block_bio_queue") $q:struct request_queue* $bio:struct bio*
kernel.trace("block_bio_frontmerge") $q:struct request_queue* $bio:struct bio*