Make min(x, y) equal to (x < y ? x : y) and max(x, y) equal to
(x > y ? x : y), including the behavior for signed zeros and NaNs.
This also enables optimizing them into min and max SSE2 instructions
on x86.

Bug swiftshader:19

Change-Id: I047b90e9da9f3c72657ab7c619bc91b92a700a45
Reviewed-on: https://swiftshader-review.googlesource.com/8771Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>