[WINED3D: Review] Hook software shaders into drawStridedSlow

[Ivan Gyurdiev]

To make it clear, this doesn't implement software shaders - it just 
moves code around so when they're implemented it would be easier to do.

I already have one more or less working implementation, but it's based 
on executing small functions for each opcode (like the previous code 
does), except it goes through central processing with hardware shaders. 
That's incredibly slow.... so more thought needs to go into how shaders 
can be implemented. If it was possible to pre-generate the shader code 
(in asm?) somehow that'd be nice...

However shaders are implemented though, I think they should hook into 
the rest of the code as shown in the patch.