BugID: 781

Checkin comment for previous (mistaken) checkin.

Allow specification of negative --integration. This is handy to allow saving
statistics during a long period with an interval > 1 sec but without integration:

E.g. ./rspctl --statis=beamlet --select=0,1 --duration=3600 --integration=-10

Would save beamlet statistics every 10 seconds for a period of 3600 seconds (360 spectra are saved).
The spectrum is sampled/saved every 10 seconds without integrating over the 10 second period.