Bug 839: Clarifying GLStateTracker.clearStates(..) remove 'enable' change - Part 1

TODO: Only disable state tracker at GLContext.destroy()
Fix Bug 826: GLJPanel: Fully restore TextureState and Viewport

In FBO mode save TextureState of current texture-unit,
as well as for the fbo texture-unit if the latter is a different.

In glslTextureRaster mode for verical flip (using FBO),
set the viewport to drawable size if before flipping and restore afterward - if equired.

TestGLJPanelTextureStateAWT fully tests use cases:
  - Keep texture bound w/ same or other texture-unit
  - Use 2 viewports within one drawable and keep it
AWT Printing: Fix non vertical-flipped printing, i.e. cut-off top-row's tile upper area, cleanup.

TestTiledPrintingGearsSwingAWT2: Provoked !flipped bug where top-row was positioned too low
due to using full size tile-height.

Cutting of the unused top-row's upper area corrects this issue.

vertical-flip mode does not expose this situation, since flipping
shifts the payload to the upper tile area.

TestTiledPrintingGearsSwingAWT2: Also tests an alternative transparent overlapping mode
without layout.