These break dynamic loading of OpenGL ES and bloat OpenTK.dll with
duplicated strings. The new extension loading mechanism is now fast
enough to make DllImports unnecessary.
We can use DllImports for OpenGL functions <= v1.1 on all platforms,
including Windows. This allows us to reduce the number of required
GetProcAddress calls by 474, reducing startup time and memory
consumption.
This setting can be turned off through Settings.Legacy.UseDllImports
and UseWindowsCompatibleGL.