Use int32 for parameter block sizes.

CostFunction now uses int32 instead of int16
to store the size of its parameter blocks.

This is an API breaking change.

Change-Id: I032ea583bc7ea4b3009be25d23a3be143749c73e
diff --git a/include/ceres/dynamic_numeric_diff_cost_function.h b/include/ceres/dynamic_numeric_diff_cost_function.h
index c2bfb32..2b6e826 100644
--- a/include/ceres/dynamic_numeric_diff_cost_function.h
+++ b/include/ceres/dynamic_numeric_diff_cost_function.h
@@ -104,7 +104,7 @@
         << "You must call DynamicNumericDiffCostFunction::SetNumResiduals() "
         << "before DynamicNumericDiffCostFunction::Evaluate().";
 
-    const vector<int16>& block_sizes = parameter_block_sizes();
+    const vector<int32>& block_sizes = parameter_block_sizes();
     CHECK(!block_sizes.empty())
         << "You must call DynamicNumericDiffCostFunction::AddParameterBlock() "
         << "before DynamicNumericDiffCostFunction::Evaluate().";