Fix evaluation of initial cost and corresponding test

Commit f102a68e411d11b4864e17b69a2d781e9c2692ad seems to have introduced
a bug in both solver_impl.cc and solver_impl_test.cc
solver_impl_test showed 3 errors, where two were due to ceres NOT
failing when the test expected that, and one was due to the initial cost
being wrong (-1 instead of 0.5)
Ceres now does not attempt to evaluate the initial cost if
options.return_initial_xxx is not set. It therefore did not fail in
the tests.
It also seems that the CERES_EVALUATE macro erroneously always sets
final_cost, even when called with 'initial' as argument.

Change-Id: Ia3c3eeb476e7023a3f80b201124010d6c67e9824

internal/ceres/solver_impl.cc

diff --git a/internal/ceres/solver_impl.cc b/internal/ceres/solver_impl.cc
index a070ce6..475e71d 100644
--- a/internal/ceres/solver_impl.cc
+++ b/internal/ceres/solver_impl.cc
@@ -86,7 +86,7 @@
   Evaluator::Evaluate(                                                  \
       original_program,                                                 \
       options.num_threads,                                              \
-      &summary->final_cost,                                             \
+      &summary->which ## _cost,                                         \
       options.return_ ## which ## _residuals ? &summary->which ## _residuals : NULL, \
       options.return_ ## which ## _gradient ? &summary->which ## _gradient : NULL, \
       options.return_ ## which ## _jacobian ? &summary->which ## _jacobian : NULL)

internal/ceres/solver_impl_test.cc

diff --git a/internal/ceres/solver_impl_test.cc b/internal/ceres/solver_impl_test.cc
index d918a57..5cba7d7 100644
--- a/internal/ceres/solver_impl_test.cc
+++ b/internal/ceres/solver_impl_test.cc
@@ -859,6 +859,7 @@
   Solver::Options options;
   Solver::Summary summary;
   double x;
+  options.return_initial_residuals = true;
   problem_impl.AddResidualBlock(new FailingCostFunction, NULL, &x);
   SolverImpl::Solve(options, &problem_impl, &summary);
   EXPECT_EQ(summary.termination_type, NUMERICAL_FAILURE);
@@ -870,6 +871,8 @@
   Solver::Options options;
   Solver::Summary summary;
   double x = 1;
+  options.return_initial_residuals = true;
+  options.return_final_residuals = true;
   problem_impl.AddResidualBlock(new UnaryIdentityCostFunction, NULL, &x);
   problem_impl.SetParameterBlockConstant(&x);
   SolverImpl::Solve(options, &problem_impl, &summary);