The name d3d10_effect_variable is somewhat misleading, since these
aren't actually effect variables as returned by e.g.
ID3D10Effect::GetVariableByName(), but effect objects as referenced by
effect passes.

This was originally added as a workaround for a Mesa bug by commit
ddf52dda. The other half of the hack has since
been removed. This code causes problems when wglDeleteContext() from a
different thread causes our current context to be destroyed, since
wglGetCurrentContext() will return a destroyed context in that case. That is a
flaw in our wgl implementation, since wglDeleteContext() shouldn't allow a
context that's current in a different thread to be destroyed, but this hack is
a bad idea regardless.

Translations by Vincent Beers.

On ATI cards we use the driver's GL_ARB_texture_non_power_of_two emulation to
support conditional NP2 textures without having to deal with the denormalized
coordinates. The default GL_TEXTURE_2D address mode is incompatible with
GL_ARB_texture_rectangle however.