omniorb: bump to version 4.2.0

Also add a hash file.

The release announcement
(http://www.omniorb-support.com/pipermail/omniorb-list/2014-April/031550.html

)
mentions support for python3, but I could not make it work. Stay with python2
for now.

Cc: Matt Weber <mlweber1@rockwellcollins.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>