Add containsNaN functions in MatGeneric<Cpu> and subclasses.

src/faust_linear_operator/CPU/faust_MatDense.h

src/faust_linear_operator/CPU/faust_MatDense.hpp

src/faust_linear_operator/CPU/faust_MatDiag.h

src/faust_linear_operator/CPU/faust_MatDiag.hpp

src/faust_linear_operator/CPU/faust_MatSparse.h

src/faust_linear_operator/CPU/faust_MatSparse.hpp

src/faust_linear_operator/faust_MatGeneric.h