Fix bug in clearSubsceneList; another try at debugging problems in bgplot3d.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rgl@1152 79a1b648-8b68-254f-b20b-c0b50f5137bf
Turn off testing of bgplot3d example

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rgl@1153 79a1b648-8b68-254f-b20b-c0b50f5137bf