unix: add kernel module load/unload syscalls on Linux

InitModule loads a kernel module from an ELF image. FinitModule loads a
kernel module from a file descriptor. DeleteModule unloads a kernel
module.

These syscalls require the CAP_SYS_MODULE capability.

See http://man7.org/linux/man-pages/man2/init_module.2.html and
http://man7.org/linux/man-pages/man2/delete_module.2.html for details.

Also drop deprecated syscalls related to kernel modules from the list
of unimplemented syscalls.

Change-Id: I131e17f02c5617640f5f4073982d2b27a6d78bbf
Reviewed-on: https://go-review.googlesource.com/c/144173
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unix/mkerrors.sh

@@ -197,6 +197,7 @@ struct ltchars {
 #include <linux/keyctl.h>
 #include <linux/magic.h>
 #include <linux/memfd.h>
+#include <linux/module.h>
 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netlink.h>
 #include <linux/net_namespace.h>
@@ -449,6 +450,7 @@ ccflags="$@"
 		$2 ~ /^KEXEC_/ ||
 		$2 ~ /^LINUX_REBOOT_CMD_/ ||
 		$2 ~ /^LINUX_REBOOT_MAGIC[12]$/ ||
+		$2 ~ /^MODULE_INIT_/ ||
 		$2 !~ "NLA_TYPE_MASK" &&
 		$2 ~ /^(NETLINK|NLM|NLMSG|NLA|IFA|IFAN|RT|RTC|RTCF|RTN|RTPROT|RTNH|ARPHRD|ETH_P|NETNSA)_/ ||
 		$2 ~ /^SIOC/ ||