add internal documentation

Eigen/src/Core/Matrix.h

@@ -44,11 +44,11 @@
   *
   * \note <b>Fixed-size versus dynamic-size:</b>
   * Fixed-size means that the numbers of rows and columns are known are compile-time. In this case, Eigen allocates the array
-  * of coefficients as a fixed-size array on the stack. This makes sense for very small matrices, typically up to 4x4, sometimes up
+  * of coefficients as a fixed-size array, as a class member. This makes sense for very small matrices, typically up to 4x4, sometimes up
   * to 16x16. Larger matrices should be declared as dynamic-size even if one happens to know their size at compile-time.
   *
   * Dynamic-size means that the numbers of rows or columns are not necessarily known at compile-time. In this case they are runtime variables,
-  * and the array of coefficients is allocated dynamically, typically on the heap (See note on heap allocation below).
+  * and the array of coefficients is allocated dynamically, typically on the heap (See note on Usage of alloca() below).
   *
   * Note that dense matrices, be they Fixed-size or Dynamic-size, <em>do not</em> expand dynamically in the sense of a std::map.
   * If you want this behavior, see the Sparse module.
@@ -60,7 +60,7 @@
   * exceed a certain value. This happens when taking dynamic-size blocks inside fixed-size matrices: in this case _MaxRows and _MaxCols
   * are the dimensions of the original matrix, while _Rows and _Cols are Dynamic.
   *
-  * \note <b> Heap allocation:</b>
+  * \note <b> Usage of alloca():</b>
   * On the Linux platform, for small enough arrays, Eigen will avoid heap allocation and instead will use alloca() to perform a dynamic
   * allocation on the stack.
   *
@@ -85,7 +85,6 @@
   * v[1] = 0.2;
   * v(0) = 0.1;
   * v(1) = 0.2;
-
   *
   * Eigen::MatrixXi m(10, 10);
   * m(0, 1) = 1;