[3/8] wined3d: Create a separate function for sampling a texture

[Ivan Gyurdiev]

H. Verbeet wrote:
> There are a couple of instructions that have to sample from a texture,
> right now most of them duplicate that code, and hardcode the texture
> type.
>
> Changelog:
>  - Create a separate function for sampling a texture
You should continue to use "add_param" or "get_register_name". There 
should be a single point in the code where register names are 
constructed, adding another one is a bad idea. This function is 
specifically tasked with naming registers, and taking into account 
things like relative addressing, so that when samplers support relative 
addressing in the future, changing the naming scheme would be trivial.