Added an ei_linspaced_op to create linearly spaced vectors.

Added setLinSpaced/LinSpaced functionality to DenseBase.
Improved vectorized assignment - overcomes MSVC optimization issues.
CwiseNullaryOp is now requiring functors to offer 1D and 2D operators.
Adapted existing functors to the new CwiseNullaryOp requirements.
Added ei_plset to create packages as [a, a+1, ..., a+size].
Added more nullaray unit tests.

Eigen/src/Core/util/Constants.h

@@ -224,6 +224,11 @@ namespace {
   EIGEN_UNUSED NoChange_t NoChange;
 }
 
+struct Sequential_t {};
+namespace {
+  EIGEN_UNUSED Sequential_t Sequential;
+}
+
 struct Default_t {};
 namespace {
   EIGEN_UNUSED Default_t Default;