This confuses applications like Steam, which hook d3d9 and opengl
functions. It sees that the application uses opengl32, but it doesn't
realize that d3d9 is wrapped to opengl. Thus it starts messing around
with wined3d's wgl context. It usually tries to draw geometry with the
context, but cannot deal with some of the obscure extensions we have
activated.

Otherwise it will be 0 if GL_ARB_multitexture is not available.

They're not needed, they are handled by the state management anyway.

We cannot remove this because we still have to load the surface as
RGB. The shader may take care of setting the blue channel to 1.0 now,
but we still get the red and green channels loaded incorrectly if we
don't insert a blue channel before loading.

The RichEditWndProc_common function is big enough already by handling
all the window messages, so moving code to handle a message to its own
function makes the code more readable.