[PATCH] Support for live tracing

[PATCH] Support for live tracing

This patch adds support for doing live traces again, by allowing pipe of
data from blktrace to blkparse. A structural change was needed in blk_io_trace
to pass the CPU number info directly instead of inferring it from the filename.

To parse realtime:

$ blktrace -d /dev/xxx -o - | blkparse -i -