debugstencil var


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1609 b412e182-2ed4-4078-95c4-27dc59f57fa9
avoid extra g-buffer color clear when no stencil is available for transparent pass


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1610 b412e182-2ed4-4078-95c4-27dc59f57fa9