This also makes us a bit more accurate, due to better rounding of
intermediate results.
This also gives us the flush-to-zero and denormals-are-zero SSE settings
for free! (Assuming UE is build with SSE)
This almost fully implements the SSE extension, similar to the x87 and
MMX extensions, using a separate class "SoftVPU".
Currently missing are all shadow and exception checks, as well as the
denormals-are-zero and flush-to-zero flags.
Also missing are some integer-SIMD functions.
