[PATCH] blkparse: Add option to hash process by name

[PATCH] blkparse: Add option to hash process by name

For some traces, you really don't want to see thousands of cc1
processes in the stats, you want to collect the stats by name
instead. This adds the -n option to blkparse, enabling that.

Switched to Jenkins hash at the same time, as it allows for
easy hash-by-u32 or hash-by-name as we see fit.