Fixed compilation error of irtkMatrix.h on MAc regarding friend declarations
Fixed compilation error of irtkMatrix.h on MAc regarding friend declarations

BioMedIA/irtk-legacy,ghisvail/irtk-legacy,BioMedIA/irtk-legacy,BioMedIA/IRTK,BioMedIA/irtk-legacy,ghisvail/irtk-legacy,ghisvail/irtk-legacy,BioMedIA/IRTK,BioMedIA/IRTK,BioMedIA/irtk-legacy,ghisvail/irtk-legacy,BioMedIA/IRTK