Updating MonoGame to use OpenGL on Windows.

Summary: According to @Sabre070, the combination of this change and manually copying the Content folder to `Tychaia/bin/Debug` makes the game run under Windows.  Future steps are to make `Tychaia.Content/compiled/Content` copy automatically on Windows.

Test Plan:
  # Apply the patch
  # Regenerate projects
  # Rebuild
  # Copy the Content folder
  # Run Tychaia.exe

Reviewers: Sabre070

Reviewed By: Sabre070

Maniphest Tasks: T7, T16

Differential Revision: http://code.redpointsoftware.com.au/D16