MERGE: fix subnormal test on AMD64 (2nd attempt)

[Stefan Westerfeld <stefan space twc de>]

   Hi!

Since on AMD64, denormals are treated as zero (a feature of SSE math), the
subnormals test breaks. My previous merge request was not accepted, because it
didn't check the CPU status registers, but just assumed that if a certain
calculation resulted in 0, CPU would be in DAZ mode.

So in my new attempt to fix this, I check the CPU status registers. I also
check if the SSE unit is actually used for floating point math by checking
x86_64 and FLT_EVAL_METHOD defines.

repo:   http://space.twc.de/public/git/stwbeast.git
branch: subnormals2-amd64

   Cu... Stefan
-- 
Stefan Westerfeld, Hamburg/Germany, http://space.twc.de/~stefan