unix: add Linux block device ioctl types and constants

These types and constants are taken from hdreg.h, and will enable
querying and manipulation of block devices on Linux.

Fixes golang/go#24971

Change-Id: Iafe8f81ba7ab9f1e127743dab6a9fb1912874a5c
Reviewed-on: https://go-review.googlesource.com/108455
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

unix/mkerrors.sh

@@ -189,6 +189,7 @@ struct ltchars {
 #include <linux/genetlink.h>
 #include <linux/stat.h>
 #include <linux/watchdog.h>
+#include <linux/hdreg.h>
 #include <net/route.h>
 #include <asm/termbits.h>
 
@@ -436,6 +437,7 @@ ccflags="$@"
 		$2 ~ /^ATTR_(BIT_MAP_COUNT|(CMN|VOL|FILE)_)/ ||
 		$2 ~ /^FSOPT_/ ||
 		$2 ~ /^WDIOC_/ ||
+		$2 ~ /^(HDIO|WIN|SMART)_/ ||
 		$2 !~ "WMESGLEN" &&
 		$2 ~ /^W[A-Z0-9]+$/ ||
 		$2 ~ /^BLK[A-Z]*(GET$|SET$|BUF$|PART$|SIZE)/ {printf("\t%s = C.%s\n", $2, $2)}