Xtof : correction of compilation issues about PoldiAutoCorrelation5.h

issues about the compilation of the file with different compiler has been fixed, using the PhysicalConstant.h library...
no more constant are declared inside the class now, and the algorithm refert directly to the constants declared by mantid, including for pi

warning fixed about deprecated Algo declaration
	modified:   Code/Mantid/Framework/PythonInterface/plugins/algorithms/ViewBOA.py

PhysicalConstant.h is now used to declare constants
	modified:   Code/Mantid/Framework/SINQ/inc/MantidSINQ/PoldiAutoCorrelation5.h
	modified:   Code/Mantid/Framework/SINQ/src/PoldiAutoCorrelation5.cpp

Refs #100