Support reading from multiple files

[skeggse]

error: The argument '--file <file>' was provided more than once, but cannot be used multiple times

USAGE:
    agrind --file <file> <query>

For more information try --help

If you've got a collection of log files, it can be nice to not have to concatenate them first (and might work well with concurrent parsing to avoid a linearization bottleneck?)

[rcoh]

reasonable feature, I think.

[rcoh]

fyi, parsing is single threaded at the moment, the full input stream is deterministically ordered