Include the MXCSR initial values, based on the AMD docs. This file

should really be renamed to fpu.h and npx.c to fpu.c since its part of
the core architecture on amd64 systems, not an isa 'numeric processor
extension'.

sys/amd64/include/fpu.h

@@ -95,6 +95,8 @@ struct  savefpu {
  * intermediate values are stored in memory or in FPU registers.
  */
 #define	__INITIAL_NPXCW__	0x127F
+#define	__INITIAL_MXCSR__	0x1F80
+#define	__INITIAL_MXCSR_MASK__	0xFFBF
 
 #ifdef _KERNEL
 int	npxdna(void);

sys/amd64/include/npx.h

@@ -95,6 +95,8 @@ struct  savefpu {
  * intermediate values are stored in memory or in FPU registers.
  */
 #define	__INITIAL_NPXCW__	0x127F
+#define	__INITIAL_MXCSR__	0x1F80
+#define	__INITIAL_MXCSR_MASK__	0xFFBF
 
 #ifdef _KERNEL
 int	npxdna(void);