Fix missing standard library headers for independent compilation (#184)

[pacortusaez05]

Hi @vissarion and @elias ! I am a Math & CS undergraduate student from the University of Murcia, Spain, and I'm very interested in participating in GSoC this year, specifically for the Benchmark Polytope Import Suite project.

To get familiar with the codebase and the contribution workflow, I started working on Issue #184. I found that independent compilation fails for some headers due to missing standard library includes.

In this PR, I have added the missing includes to the following files:

<iostream> and <ostream> to corre_matrix.hpp

<list> to sliding_window.hpp

<cmath> to boundary_cdhr_walk.hpp (as Vissarion suggested in the issue comments).

Looking forward to your feedback. Let me know if you need me to change anything!