qt modules and the new qt opengl interface

[blobfish]

FYI: I was fighting a windows 10 build and came across something. I am building with a custom meson.build and not using cmake so others might not have come across this, but I think it is worth mentioning. With osgQts rework with the new Qt opengl interface, the required modules need to be updated. The QOpengl module is not used anymore. QOpenGLWindow is part of the gui module. QOpenGLWidget is part of the widgets module. I also needed to add the core module. For reference, here is the module list from my meson.build file. qt5 = dependency('Qt5', version : '>=5.11.3', modules : ['core', 'widgets', 'gui'])