fix x32 __set_thread_area failure due to junk in upper bits

the kernel does not properly clear the upper bits of the syscall
argument, so we have to do it before the syscall.

src/thread/x32/__set_thread_area.s

@@ -3,7 +3,7 @@
 .global __set_thread_area
 .type __set_thread_area,@function
 __set_thread_area:
-	mov %rdi,%rsi           /* shift for syscall */
+	mov %edi,%esi           /* shift for syscall */
 	movl $0x1002,%edi       /* SET_FS register */
 	movl $0x4000009e,%eax          /* set fs segment to */
 	syscall                 /* arch_prctl(SET_FS, arg)*/