The opengl extension mentioned in that code was never finished, and as
far as I know there is no way to make use of tangent data in the d3d
fixed function pipeline as well.

Note that GL_ATI_envmap_bumpmap is not the same as
GL_ATI_fragment_shader. envmap_bumpmap is used together with the
regular opengl ffp pipeline and is not used (other than for
pixelformats) if GL_ATI_fragment_shader is used.

Removes unnecessary and unsafe type assignment, adds a missing VariantClear.

Spotted by Dan Kegel.