szip: new package

[Thomas:
  - Add hash file.
  - Rewrap Config.in help text and remove trailing whitespace.
  - Remove unneeded empty new line at the end of the .mk file.]

Signed-off-by: Ernesto L. Williams Jr <ernesto@slac.stanford.edu>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>