fix compilation of the doc and started a page dedicated to high performance and or BLAS users

doc/snippets/HouseholderQR_solve.cpp

@@ -4,6 +4,6 @@ Matrix3f y = Matrix3f::Random();
 cout << "Here is the matrix m:" << endl << m << endl;
 cout << "Here is the matrix y:" << endl << y << endl;
 Matrix3f x;
-m.householderQr().solve(y, &x));
+m.householderQr().solve(y, &x);
 assert(y.isApprox(m*x));
 cout << "Here is a solution x to the equation mx=y:" << endl << x << endl;

doc/snippets/MatrixBase_asDiagonal.cpp

@@ -1 +1 @@
-cout << Vector3i(2,5,6).asDiagonal() << endl;
+cout << Matrix3i(Vector3i(2,5,6).asDiagonal()) << endl;

doc/snippets/MatrixBase_extract.cpp

@@ -1,3 +1,5 @@
+#warning deprecated
+/* deprecated
 Matrix3i m = Matrix3i::Random();
 cout << "Here is the matrix m:" << endl << m << endl;
 cout << "Here is the upper-triangular matrix extracted from m:" << endl
@@ -6,3 +8,4 @@ cout << "Here is the strictly-upper-triangular matrix extracted from m:" << endl
      << m.part<Eigen::StrictlyUpperTriangular>() << endl;
 cout << "Here is the unit-lower-triangular matrix extracted from m:" << endl
      << m.part<Eigen::UnitLowerTriangular>() << endl;
+*/

doc/snippets/MatrixBase_marked.cpp

@@ -1,3 +1,5 @@
+#warning deprecated
+/*
 Matrix3d m = Matrix3d::Zero();
 m.part<Eigen::UpperTriangular>().setOnes();
 cout << "Here is the matrix m:" << endl << m << endl;
@@ -7,3 +9,4 @@ cout << "Here is the matrix n:" << endl << n << endl;
 cout << "And now here is m.inverse()*n, taking advantage of the fact that"
         " m is upper-triangular:" << endl
      << m.marked<Eigen::UpperTriangular>().solveTriangular(n);
+*/

doc/snippets/MatrixBase_part.cpp

@@ -1,3 +1,5 @@
+#warning deprecated
+/*
 Matrix3d m = Matrix3d::Zero();
 m.part<Eigen::StrictlyUpperTriangular>().setOnes();
 cout << "Here is the matrix m:" << endl << m << endl;
@@ -6,3 +8,4 @@ cout << "And let us now compute m*m.adjoint() in a very optimized way" << endl
 Matrix3d n;
 n.part<Eigen::SelfAdjoint>() = (m*m.adjoint()).lazy();
 cout << "The result is:" << endl << n << endl;
+*/