Miscellanous fixes in preparation for 1.6.0

1. Bug fix in NumericDiffCostFunction (Thanks to Nicolas Brodu).
2. Minor documentation update in solver.h
3. Version history update.
4. Bump the version and ABI version.

Change-Id: I951574ddd0b2c4c03b9c79ff33eb9bea549071e7
diff --git a/include/ceres/ceres.h b/include/ceres/ceres.h
index ac76e97..b7aeeef 100644
--- a/include/ceres/ceres.h
+++ b/include/ceres/ceres.h
@@ -34,8 +34,8 @@
 #ifndef CERES_PUBLIC_CERES_H_
 #define CERES_PUBLIC_CERES_H_
 
-#define CERES_VERSION 1.5.0
-#define CERES_ABI_VERSION 1.5.0
+#define CERES_VERSION 1.6.0
+#define CERES_ABI_VERSION 1.6.0
 
 #include "ceres/autodiff_cost_function.h"
 #include "ceres/autodiff_local_parameterization.h"
diff --git a/include/ceres/numeric_diff_cost_function.h b/include/ceres/numeric_diff_cost_function.h
index 555bc3d..4c84d4c 100644
--- a/include/ceres/numeric_diff_cost_function.h
+++ b/include/ceres/numeric_diff_cost_function.h
@@ -230,8 +230,8 @@
     if (N5) parameters_reference_copy[5] = parameters_reference_copy[4] + N4;
     if (N6) parameters_reference_copy[6] = parameters_reference_copy[5] + N5;
     if (N7) parameters_reference_copy[7] = parameters_reference_copy[6] + N6;
-    if (N7) parameters_reference_copy[8] = parameters_reference_copy[7] + N7;
-    if (N8) parameters_reference_copy[9] = parameters_reference_copy[8] + N8;
+    if (N8) parameters_reference_copy[8] = parameters_reference_copy[7] + N7;
+    if (N9) parameters_reference_copy[9] = parameters_reference_copy[8] + N8;
 
 #define COPY_PARAMETER_BLOCK(block)                                     \
   if (N ## block) memcpy(parameters_reference_copy[block],              \
diff --git a/include/ceres/solver.h b/include/ceres/solver.h
index 8e3fa58..0603a30 100644
--- a/include/ceres/solver.h
+++ b/include/ceres/solver.h
@@ -351,9 +351,6 @@
     // deallocate the memory when destroyed.
     ParameterBlockOrdering* linear_solver_ordering;
 
-    // Note: This option only applies to the SPARSE_NORMAL_CHOLESKY
-    // solver when used with SUITE_SPARSE.
-
     // Sparse Cholesky factorization algorithms use a fill-reducing
     // ordering to permute the columns of the Jacobian matrix. There
     // are two ways of doing this.