add: clipplanecaps example with VisitSubTree

Example contributed by Johannes Brunen, many thanks!
changed: split traversal validation and traversal data storage
fixed:   compute algo elem memory leak
         simple shl chunk typo
fixed: win compile problems
added: initial compute shader example (textures only)
fixed: use osg extension handling (glBindImageTexture)
fixed: added missing generated parser/scanner files
fixed: determing internal format if not set for TextureImageChunk
fixed: flexlexer include
fixed: win link problems
skinning in cluster mode fix
GPU skinning sych fix 2
fixed: compile errors (signed/unsigned)