Add the ability to query the Problem about parameter blocks.

Change-Id: Ieda1aefa28e7a1d18fe6c8d1665882e4d9c274f2
diff --git a/internal/ceres/problem_impl.h b/internal/ceres/problem_impl.h
index ccc315d..2609389 100644
--- a/internal/ceres/problem_impl.h
+++ b/internal/ceres/problem_impl.h
@@ -139,6 +139,10 @@
   int NumResidualBlocks() const;
   int NumResiduals() const;
 
+  int ParameterBlockSize(double* parameter_block) const;
+  int ParameterBlockLocalSize(double* parameter_block) const;
+  void GetParameterBlocks(vector<double*>* parameter_blocks) const;
+
   const Program& program() const { return *program_; }
   Program* mutable_program() { return program_.get(); }