Allow to filter proc/fd results by size.

So now you can just check the seex status of any large files:

    cv -gc \* -S $((1024*1024*1024))

TODO: Implement size suffixes like 1M, 1m, 1G etc.

This argument is probably of dubious worth, but it wasn't hard to add it
anyway.
Allow passing human readable sizes to --size.

This is a lot nice than raw bytes.