Following c code used in the trevor_c2 C agent.

https://github.com/littlstar/b64.c.git
    - b64.h
    - encode.c
    - decode.c
https://github.com/B-Con/crypto-algorithms.git
    - sha256.h
    - sha256.c
https://github.com/kokke/tiny-AES-c.git
    - aes.c
    - aes.h
