Sort out file size suffixes

[joel-wright]

The K, G ... size suffixes should really be using powers of 1000.

I realise that there is still mixed use, but OS X at least has been using the decimal version to report file sizes since 10.6, although Microsoft do seem to be ploughing on ignoring the standards ;)

[joel-wright]

Ok, the full situation is this:

OS X Finder: powers of 10
BSD ls (OS X terminal): powers of 2 (but can be configured to display powers of 10)
GNU coreutils 8.21 (arch linux): powers of 10 (but docs say it should be powers of 2 until configured)
Windows: always powers of 2