The OpenBSD test regress/lib/libm/fenv prints strange values from
the Intel and AMD FPU using the libm function fegetenv(3).  Implement
more detailed checks.

Load the FPU enviroment directy after exec with an assembly program.
Get the FPU default FPU status from libm.
Load the FPU enviroment with fegetenv(3).
Read the FPU storage area from proc0 via /dev/mem.