Added preprocessor definitions for the architecture details of the DLLs

Change-Id: I473d9f83cceb53247c407a5c7e30acd8346c6b40
Reviewed-on: https://swiftshader-review.googlesource.com/3033
Tested-by: Maxime Grégoire <mgregoire@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>