Cmake update and adding WINCOMPILE.md

[Hellae]

The Cmake change on microhttpd uses the working code from xmr-stak-cpu WINCOMPILE.md is based on the cpu one, but its updated with an extra set of instructions.

[psychocrypt]

Thx for the pull request. We are not accepting PR against the master branch. We use for all development the dev branch. Never the less we will release in a week the new xmr-stak where all compile changes for windows are included. Sry for the complicated release way but we refactored the full miner, therefore we used a new reposetory.