Use reflect.Value.Pointer() to compare pointers

[AlexanderYastrebov]

Summary

Use reflect.Value.Pointer() to compare pointers

Changes

Updates samePointers implementation and adds test cases

Motivation

This is needed to check if map, slice and other built-in types point to the same value

Related issues

Fixes #1076

[stevenh]

@dolmen quick ping as @AlexanderYastrebov has updated based on your feedback