ASIO is now GPL compatible so there is no longer a need to be constrained to Steinberg's proprietary licence ageement, as stated in COMPILING.md

We should continue to display their copyright statement as we currently do, and may as well comply with their request to use their logo.

Do we need to retain this copy of the agreement in the repo? We should now move to using the GPL, remove the current licence agreement from the repo, and inform Steinberg of this.