erm.. use EIGEN_ONLY_USED_FOR_DEBUG() as it already exists.

Eigen/src/Core/DenseBase.h

diff --git a/Eigen/src/Core/DenseBase.h b/Eigen/src/Core/DenseBase.h
index 3e2bcaf..e2429be 100644
--- a/Eigen/src/Core/DenseBase.h
+++ b/Eigen/src/Core/DenseBase.h
@@ -214,9 +214,7 @@
       */
     void resize(int size)
     {
-#ifdef EIGEN_NO_DEBUG
-      EIGEN_ARG_UNUSED(size); 
-#endif
+      EIGEN_ONLY_USED_FOR_DEBUG(size);
       ei_assert(size == this->size()
                 && "DenseBase::resize() does not actually allow to resize.");
     }
@@ -226,10 +224,8 @@
       */
     void resize(int rows, int cols)
     {
-#ifdef EIGEN_NO_DEBUG
-      EIGEN_ARG_UNUSED(rows); 
-      EIGEN_ARG_UNUSED(cols); 
-#endif
+      EIGEN_ONLY_USED_FOR_DEBUG(rows); 
+      EIGEN_ONLY_USED_FOR_DEBUG(cols); 
       ei_assert(rows == this->rows() && cols == this->cols()
                 && "DenseBase::resize() does not actually allow to resize.");
     }

Eigen/src/Core/TriangularMatrix.h

diff --git a/Eigen/src/Core/TriangularMatrix.h b/Eigen/src/Core/TriangularMatrix.h
index 632acc2..3eb52a5 100644
--- a/Eigen/src/Core/TriangularMatrix.h
+++ b/Eigen/src/Core/TriangularMatrix.h
@@ -89,10 +89,8 @@
 
     void check_coordinates(int row, int col)
     {
-#ifdef EIGEN_NO_DEBUG
-      EIGEN_ARG_UNUSED(row); 
-      EIGEN_ARG_UNUSED(col); 
-#endif
+      EIGEN_ONLY_USED_FOR_DEBUG(row);
+      EIGEN_ONLY_USED_FOR_DEBUG(col);
       ei_assert(col>=0 && col<cols() && row>=0 && row<rows());
       ei_assert(   (Mode==Upper && col>=row)
                 || (Mode==Lower && col<=row)

Eigen/src/Core/util/Macros.h

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index 9b27712..7871824 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -172,8 +172,6 @@
 #define EIGEN_UNUSED
 #endif
 
-#define EIGEN_ARG_UNUSED(x) (void)x;
-
 #if (defined __GNUC__)
 #define EIGEN_ASM_COMMENT(X)  asm("#"X)
 #else