simplifications in the ei_solve_impl system, factor out some boilerplate code
diff --git a/doc/snippets/FullPivLU_solve.cpp b/doc/snippets/FullPivLU_solve.cpp
index ade2697..696f414 100644
--- a/doc/snippets/FullPivLU_solve.cpp
+++ b/doc/snippets/FullPivLU_solve.cpp
@@ -2,7 +2,7 @@
Matrix2f y = Matrix2f::Random();
cout << "Here is the matrix m:" << endl << m << endl;
cout << "Here is the matrix y:" << endl << y << endl;
-Matrix<float,3,2> x = m.lu().solve(y);
+Matrix<float,3,2> x = m.fillPivLu().solve(y);
if((m*x).isApprox(y))
{
cout << "Here is a solution x to the equation mx=y:" << endl << x << endl;