Document how to use a custom OpenGL Library under Windows. This relies on Bug 1510. Be more careful within `WindowsAWTWGLGraphicsConfigurationFactory::chooseGraphicsConfigurationImpl`, i.e. don't use an invalid PixelFormatID.
Added `doc/Windows_Custom_OpenGL.md` and added notion in Windows test launch scripts - make/scripts/tests-x64.bat - make/scripts/tests-x64-dbg.bat