add SSE path for Matrix4f inverse, taken from Intel except that we do a kosher

division instead of RCPPS-followed-by-Newton-Raphson. The rationale for that is
that elsewhere in Eigen we dont allow ourselves this approximation (which throws
2 bits of mantissa), so there's no reason we should allow it here.

Eigen/LU

@@ -25,6 +25,7 @@ namespace Eigen {
 #include "src/LU/PartialPivLU.h"
 #include "src/LU/Determinant.h"
 #include "src/LU/Inverse.h"
+#include "src/LU/arch/Inverse_SSE.h"
 
 } // namespace Eigen