Solve No Previous Prototype GCC warning

In some cases there were missing includes of own
header files from implementation files.

In other cases moved function which are only used
within single file into an anonymous namespace.

Change-Id: I2c6b411bcfbc521e2a5f21265dc8e009a548b1c8
diff --git a/internal/ceres/linear_least_squares_problems.cc b/internal/ceres/linear_least_squares_problems.cc
index bc6ff00..6c886a1 100644
--- a/internal/ceres/linear_least_squares_problems.cc
+++ b/internal/ceres/linear_least_squares_problems.cc
@@ -573,6 +573,7 @@
   return problem;
 }
 
+namespace {
 bool DumpLinearLeastSquaresProblemToConsole(const string& directory,
                                             int iteration,
                                             const SparseMatrix* A,
@@ -732,6 +733,7 @@
   WriteStringToFileOrDie(matlab_script, matlab_filename);
   return true;
 }
+}  // namespace
 
 bool DumpLinearLeastSquaresProblem(const string& directory,
                                    int iteration,