Preprocessor test added to be sure that Eigen is not included before BTK.
Preprocessor test added to be sure that Eigen is not included before BTK.

letaureau/b-tk.core,xyproto/b-tk.core,xyproto/b-tk.core,xyproto/b-tk.core,xyproto/b-tk.core,xyproto/b-tk.core,letaureau/b-tk.core,Biomechanical-ToolKit/BTKCore,letaureau/b-tk.core,letaureau/b-tk.core,Biomechanical-ToolKit/BTKCore,letaureau/b-tk.core,xyproto/b-tk.core,Biomechanical-ToolKit/BTKCore,xyproto/b-tk.core,Biomechanical-ToolKit/BTKCore,letaureau/b-tk.core,Biomechanical-ToolKit/BTKCore,Biomechanical-ToolKit/BTKCore,Biomechanical-ToolKit/BTKCore,letaureau/b-tk.core,Biomechanical-ToolKit/BTKCore,letaureau/b-tk.core,xyproto/b-tk.core