Fix Windows bootstrap: check_sse2 was not DLLEXPORT

vm/cpu-x86.32.S

@@ -40,7 +40,7 @@ DEF(void,set_callstack,(F_STACK_FRAME *to, F_STACK_FRAME *from, CELL length, voi
 	ret                                /* return _with new stack_ */
 
 /* cpu.x86.32 calls this */
-DEF(bool,check_sse2,()):
+DEF(bool,check_sse2,(void)):
 	push %ebx
 	mov $1,%eax
 	cpuid

vm/cpu-x86.32.h

@@ -5,3 +5,4 @@ register CELL rs asm("edi");
 
 #define F_FASTCALL __attribute__ ((regparm (2)))
 
+DLLEXPORT bool check_sse2(void);