OST support

[mooijtech]

Support OST files (uses extended byte sizes).

[mooijtech]

• OST support:
  • OST 2013 file format: Reading the NBT in OST files from Outlook 2013
  • OST 2013 File Format – The missing documentation

[mooijtech]

Use https://github.com/klauspost/readahead for ZLib added to the format

[mooijtech]

References https://github.com/klauspost/compress