build options for gles and clang-tidy cleanup

[jwinarske]

This PR:

• Adds CMake build options: MBGL_WITH_GLES2, MBGL_WITH_GLX. This provides isolation between X11 and Wayland builds.
• mbgl-glfw links against Wayland libs if available. So if GLFW3 is built with GLFW_USE_WAYLAND=ON, it will link and run on Wayland.
• Clang-Tidy cleanup in linux/glfw related files
• Moves mbgl-glfw to es3

Tested on Fedora 33 workstation.