Add Problem::SetParameterLowerBound and Problem::SetParameterUpperBound.

These two methods allow the user to associate upper and lower bounds
with individual parameters inside parameter blocks.

Change-Id: I68dc37f20b64408da510ba06b89a4f08df54ddad

internal/ceres/problem_impl.h

diff --git a/internal/ceres/problem_impl.h b/internal/ceres/problem_impl.h
index da50578..75bdc2b 100644
--- a/internal/ceres/problem_impl.h
+++ b/internal/ceres/problem_impl.h
@@ -129,6 +129,9 @@
                            LocalParameterization* local_parameterization);
   const LocalParameterization* GetParameterization(double* values) const;
 
+  void SetParameterLowerBound(double* values, int index, double lower_bound);
+  void SetParameterUpperBound(double* values, int index, double upper_bound);
+
   bool Evaluate(const Problem::EvaluateOptions& options,
                 double* cost,
                 vector<double>* residuals,