*Better handling of optional libs for ffmpeg, and is now able to check and give user additional link libs for ffmpeg.
*Added two helpers (only used by RPM for now) to:
**check whether a version number is greater or equal than another one, and...
**check whether a version number is "included" into another one (eg 3.3.2 is included into more general 3.3).
*Added date-time as target when building our own boost.
*Removed apt-get upgrade action for DEB (let the user decide when he wants to globally upgrade its system!).