Known bugs and limitations in PLIB version 1.6.0

More in depth stuff can be found in TODO_AFTER135.

  * ssgLOS is really broken.

  * ssgStripify and ssgFlatten might well have bugs in them.
    A known bug of ssgStripify is that : since it rearranges and 
    merges leaf nodes, ssgSelectors are messed up

  * Sometimes cr*p values appear in 3D files, for example .ac files.
    The reason seems to be that sometimes the loader handles colours
    differently than the writer.

  * Several, general smalish .MDL loader bugs are known; Look in TODO_AFTER135

  * Scaling does not work (intentionally). Uniform scaling may be
    enabled by uncommenting "radius *= sgLengthVec3(m[0])" in
    sgSphere::orthoXform. It is currently disabled because that extra
    calculation would degrade performance on non-scaled matrices.
    Scaling really makes a mess of SSG bounding sphere tests

  * .ssg files should not be used for long term storage. It will probably
    change in incompatible ways.

