Check that ordinal types are signed

This is required by several algorithms and is true of the possible ETI
types. Having an unsigned ordinal gives warnings now. It might take some
work to make it fully support unsigned.

src/common/KokkosKernels_Handle.hpp

@@ -61,6 +61,10 @@ namespace Experimental {
 template <class size_type_, class lno_t_, class scalar_t_, class ExecutionSpace,
           class TemporaryMemorySpace, class PersistentMemorySpace>
 class KokkosKernelsHandle {
+  static_assert(std::is_signed<lno_t_>::value,
+                "KokkosKernelsHandle requires that lno_t_ (ordinal) is a "
+                "signed integer type.");
+
  public:
   typedef typename ExecutionSpace::execution_space HandleExecSpace;
   typedef typename TemporaryMemorySpace::memory_space HandleTempMemorySpace;

src/sparse/KokkosSparse_BlockCrsMatrix.hpp

@@ -410,6 +410,10 @@ template <class ScalarType, class OrdinalType, class Device,
           class SizeType     = typename Kokkos::ViewTraits<OrdinalType*, Device,
                                                        void, void>::size_type>
 class BlockCrsMatrix {
+  static_assert(
+      std::is_signed<OrdinalType>::value,
+      "BlockCrsMatrix requires that OrdinalType is a signed integer type.");
+
  private:
   typedef
       typename Kokkos::ViewTraits<ScalarType*, Device, void,

src/sparse/KokkosSparse_BsrMatrix.hpp

@@ -344,6 +344,10 @@ template <class ScalarType, class OrdinalType, class Device,
           class SizeType     = typename Kokkos::ViewTraits<OrdinalType*, Device,
                                                        void, void>::size_type>
 class BsrMatrix {
+  static_assert(
+      std::is_signed<OrdinalType>::value,
+      "BsrMatrix requires that OrdinalType is a signed integer type.");
+
  private:
   typedef
       typename Kokkos::ViewTraits<ScalarType*, Device, void,

src/sparse/KokkosSparse_CrsMatrix.hpp

@@ -373,6 +373,10 @@ template <class ScalarType, class OrdinalType, class Device,
           class SizeType     = typename Kokkos::ViewTraits<OrdinalType*, Device,
                                                        void, void>::size_type>
 class CrsMatrix {
+  static_assert(
+      std::is_signed<OrdinalType>::value,
+      "CrsMatrix requires that OrdinalType is a signed integer type.");
+
  private:
   typedef typename Kokkos::ViewTraits<ScalarType*, Device, void,
                                       MemoryTraits>::host_mirror_space