add explicit "on the right" triangular solving,

=> no temporary when the rhs/unknows is row major

Eigen/src/Core/util/BlasUtil.h

@@ -35,7 +35,7 @@ struct ei_gebp_kernel;
 template<typename Scalar, int nr, int StorageOrder, bool PanelMode=false>
 struct ei_gemm_pack_rhs;
 
-template<typename Scalar, int mr, int StorageOrder, bool Conjugate = false>
+template<typename Scalar, int mr, int StorageOrder, bool Conjugate = false, bool PanelMode = false>
 struct ei_gemm_pack_lhs;
 
 template<

Eigen/src/Core/util/Constants.h

@@ -233,6 +233,12 @@ enum {
   DontAlign = 0x2
 };
 
+// used for the solvers
+enum {
+  OnTheLeft = 1,
+  OnTheRight = 2
+};
+
 /* the following could as well be written:
  *   enum NoChange_t { NoChange };
  * but it feels dangerous to disambiguate overloaded functions on enum/integer types.