Add the ability to order the Program using AMD.

This will allow CHOLMOD to compute the sparse
Cholesky factorization of J'J without making
a permuted copy of it.

Change-Id: I25d0e18f5957ab7fdce15c543234bb2f09db482e
diff --git a/internal/ceres/suitesparse.cc b/internal/ceres/suitesparse.cc
index 9063fa0..5138b52 100644
--- a/internal/ceres/suitesparse.cc
+++ b/internal/ceres/suitesparse.cc
@@ -397,6 +397,11 @@
   return NULL;
 }
 
+void SuiteSparse::ApproximateMinimumDegreeOrdering(cholmod_sparse* matrix,
+                                                   int* ordering) {
+  cholmod_amd(matrix, NULL, 0, ordering, &cc_);
+}
+
 }  // namespace internal
 }  // namespace ceres