Rename LinearSolverTerminationType enums.

This increases clarity, drops redundant enums and makes things
cleaner all around.

Change-Id: I761f195ddf17ea6bd8e4e55bf5a72863660c4c3b
diff --git a/internal/ceres/dense_qr_solver.cc b/internal/ceres/dense_qr_solver.cc
index f8927ae..4388357 100644
--- a/internal/ceres/dense_qr_solver.cc
+++ b/internal/ceres/dense_qr_solver.cc
@@ -111,7 +111,7 @@
                                                          rhs_.data(),
                                                          &summary.message);
   event_logger.AddEvent("Solve");
-  if (summary.termination_type == TOLERANCE) {
+  if (summary.termination_type == LINEAR_SOLVER_SUCCESS) {
     VectorRef(x, num_cols) = rhs_.head(num_cols);
   }
 
@@ -159,7 +159,7 @@
   // is good enough or not.
   LinearSolver::Summary summary;
   summary.num_iterations = 1;
-  summary.termination_type = TOLERANCE;
+  summary.termination_type = LINEAR_SOLVER_SUCCESS;
   summary.message = "Success.";
 
   event_logger.AddEvent("TearDown");