Limited POSIX threading wrapper for FreeRTOS and a working Visual Studio demo project.

Please be aware right after tagging this release, the repo was re-structure. Demo project is now moved to https://github.com/FreeRTOS/FreeRTOS-Labs.

Lab code and projects are undergoing optimizations or refactorization to improve memory usage, modularity, documentation, demo usability, or test coverage. Please expect more changes including directory restructure in this repo.

SHA256 of Lab-Project-FreeRTOS-POSIX.zip: 67a4a76590012d148c2a80d7775fadb68e77a5b0b2f9916edf4ab8ece0017094