ability to unset an arry
make PIMPL::VBO members public

so we can access them if need be
only use VBO if it's supported
trying to support multitextures

if we have use texunits than texcoord buffers, we just
wrap the buffers.
if we use less texunits than there are texcoord buffers, they will
go unnoticed...
set normals and texcoords

texcoords work, but there's still a problem with normals
invert normals so they match the original

as we have now CW vertices (rather than CCW)
initialize window (with DEPTH!)

which also fixes the rendering of light.
renamed TEXCOORD to TEXTURE