ioctl: assume that all ioctl commands have unsigned int type

In linux, ioctl command number has a 32-bit unsigned integer type:
	fs/ioctl.c:SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
If the kernel completely ignores other bits on 64-bit architectures,
why should strace care?
Let's follow the kernel and treat it as unsigned int.

* defs.h (struct_ioctlent): Change "code" type to "unsigned int".
(ioctl_decode, ioctl_lookup, block_ioctl, loop_ioctl, mtd_ioctl,
ubi_ioctl, ptp_ioctl, scsi_ioctl, sock_ioctl, term_ioctl, rtc_ioctl,
v4l2_ioctl): Likewise.
* ioctl.c (ioctl_decode, ioctl_lookup, compare, ioctl_next_match):
Likewise.
* block.c (block_ioctl): Likewise.
* loop.c (loop_ioctl): Likewise.
* mtd.c (mtd_ioctl, ubi_ioctl): Likewise.
* ptp.c (ptp_ioctl): Likewise.
* scsi.c (scsi_ioctl): Likewise.
* sock.c (sock_ioctl): Likewise.
* term.c (term_ioctl): Likewise.
* time.c (rtc_ioctl): Likewise.
* v4l2.c (v4l2_ioctl): Likewise.
* ioctlsort.c (struct ioctlent, compare, main): Likewise.
diff --git a/block.c b/block.c
index b62e436..36d7433 100644
--- a/block.c
+++ b/block.c
@@ -103,7 +103,7 @@
 }
 
 int
-block_ioctl(struct tcb *tcp, long code, long arg)
+block_ioctl(struct tcb *tcp, const unsigned int code, long arg)
 {
 	switch (code) {
 	/* take arg as a value, not as a pointer */