gendecal fix


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1946 b412e182-2ed4-4078-95c4-27dc59f57fa9
fade out backfacing decals


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1947 b412e182-2ed4-4078-95c4-27dc59f57fa9
bvec cleanup


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1948 b412e182-2ed4-4078-95c4-27dc59f57fa9
better handling of decal backfacing


git-svn-id: svn://svn.tuxfamily.org/svnroot/tesseract/main@1949 b412e182-2ed4-4078-95c4-27dc59f57fa9