Change the type of parameter index/offset to match their getter/setter

Change-Id: If28b795e792f39db9775ada105e9038570195329

internal/ceres/parameter_block.h

diff --git a/internal/ceres/parameter_block.h b/internal/ceres/parameter_block.h
index d8432c7..88943df 100644
--- a/internal/ceres/parameter_block.h
+++ b/internal/ceres/parameter_block.h
@@ -367,13 +367,13 @@
 
   // The index of the parameter. This is used by various other parts of Ceres to
   // permit switching from a ParameterBlock* to an index in another array.
-  int32_t index_ = -1;
+  int index_ = -1;
 
   // The offset of this parameter block inside a larger state vector.
-  int32_t state_offset_ = -1;
+  int state_offset_ = -1;
 
   // The offset of this parameter block inside a larger delta vector.
-  int32_t delta_offset_ = -1;
+  int delta_offset_ = -1;
 
   // If non-null, contains the residual blocks this parameter block is in.
   std::unique_ptr<ResidualBlockSet> residual_blocks_;