unix: add perf event ioctl constants on Linux

Add the PERF_EVENT_IOC_* constants on Linux which are used to
enable/disable/configure perf events. Also add the PERF_IOC_FLAG_GROUP
constant which might be using as part of the ioct argument. See section
"perf_event ioctl calls" in
http://man7.org/linux/man-pages/man2/perf_event_open.2.html

Change-Id: I92fb8f6ef5cc53711f00db566d8e277cdf1cd607
Reviewed-on: https://go-review.googlesource.com/47770
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/mkerrors.sh

@@ -166,6 +166,7 @@ struct ltchars {
 #include <linux/fs.h>
 #include <linux/keyctl.h>
 #include <linux/netlink.h>
+#include <linux/perf_event.h>
 #include <linux/random.h>
 #include <linux/reboot.h>
 #include <linux/rtnetlink.h>
@@ -404,6 +405,7 @@ ccflags="$@"
 		$2 ~ /^GRND_/ ||
 		$2 ~ /^KEY_(SPEC|REQKEY_DEFL)_/ ||
 		$2 ~ /^KEYCTL_/ ||
+		$2 ~ /^PERF_EVENT_IOC_/ ||
 		$2 ~ /^SECCOMP_MODE_/ ||
 		$2 ~ /^SPLICE_/ ||
 		$2 ~ /^(VM|VMADDR)_/ ||