fix few warnings reported by clang

Eigen/src/Core/BandMatrix.h

diff --git a/Eigen/src/Core/BandMatrix.h b/Eigen/src/Core/BandMatrix.h
index dda8efb..e7139d0 100644
--- a/Eigen/src/Core/BandMatrix.h
+++ b/Eigen/src/Core/BandMatrix.h
@@ -284,6 +284,7 @@
       : m_coeffs(coeffs),
         m_rows(rows), m_supers(supers), m_subs(subs)
     {
+      EIGEN_UNUSED_VARIABLE(cols);
       //internal::assert(coeffs.cols()==cols() && (supers()+subs()+1)==coeffs.rows());
     }
 

Eigen/src/Core/TriangularMatrix.h

diff --git a/Eigen/src/Core/TriangularMatrix.h b/Eigen/src/Core/TriangularMatrix.h
index c04fa0c..d3e195e 100644
--- a/Eigen/src/Core/TriangularMatrix.h
+++ b/Eigen/src/Core/TriangularMatrix.h
@@ -111,6 +111,7 @@
       EIGEN_ONLY_USED_FOR_DEBUG(col);
       eigen_assert(col>=0 && col<cols() && row>=0 && row<rows());
       const int mode = int(Mode) & ~SelfAdjoint;
+      EIGEN_ONLY_USED_FOR_DEBUG(mode);
       eigen_assert((mode==Upper && col>=row)
                 || (mode==Lower && col<=row)
                 || ((mode==StrictlyUpper || mode==UnitUpper) && col>row)

unsupported/Eigen/src/FFT/ei_kissfft_impl.h

diff --git a/unsupported/Eigen/src/FFT/ei_kissfft_impl.h b/unsupported/Eigen/src/FFT/ei_kissfft_impl.h
index 667638f..04b98b0 100644
--- a/unsupported/Eigen/src/FFT/ei_kissfft_impl.h
+++ b/unsupported/Eigen/src/FFT/ei_kissfft_impl.h
@@ -294,11 +294,19 @@
   inline
     void fwd2( Complex * dst,const Complex *src,int n0,int n1)
     {
+        EIGEN_UNUSED_VARIABLE(dst);
+        EIGEN_UNUSED_VARIABLE(src);
+        EIGEN_UNUSED_VARIABLE(n0);
+        EIGEN_UNUSED_VARIABLE(n1);
     }
 
   inline
     void inv2( Complex * dst,const Complex *src,int n0,int n1)
     {
+        EIGEN_UNUSED_VARIABLE(dst);
+        EIGEN_UNUSED_VARIABLE(src);
+        EIGEN_UNUSED_VARIABLE(n0);
+        EIGEN_UNUSED_VARIABLE(n1);
     }
 
   // real-to-complex forward FFT