An offscreen GLDrawable using BITMAP on Windows shall expose the same behavior than
Culprit is WindowsBitmapWGLDrawable, which flips the GDI DiB via
BITMAPINFOHEADER's height field while assigning the negative height.
This shall not be done, since we don't read out the DiB directly,
but via OpenGL.
Depends on Bug 720, since cleaning up GLContextImpl* is required to move
to 'GLDrawable.isGLOriented()' where it belongs!
Windows BITMAP GLDrawable impl. isGLOriented() shall return false,
while we keep the BITMAPINFOHEADER's height field negative
to remove the need for vertical flip when used w/ AWT or Windows, ..
Then property 'GLDrawable.isGLOriented()' has to be recognized throughout the
utility functions, i.e. TextureData's mustFlipVertically and hence TextureIO writer.