autogen: alias always-y onto always for kernel < 5.10

autogen.lua writes `always-y := dump_N.pp extract.s` to targets.mk so
kbuild builds those targets alongside the usual obj-y/obj-m chain.
`always-y` was introduced in 5.10 (f9a4210b1ab9); earlier kernels only
honor the legacy `always`. Without this alias the declaration is a
no-op on 5.4, kbuild only links built-in.a, and the first .pp file
autogen tries to read doesn't exist:

autogen.lua: cannot read .../autogen/dump_1.pp: No such file or directory

README: update passwd example to require("linux.stat")

Stat constants moved from the hardcoded linux.stat namespace table to an
autogen module (a12c0ea); callers now require "linux.stat" directly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lunatik: bump version to 4.2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

remove nop() from driver.lua

bump Lunatik version to 4.1

fix SKB resize for MAC header on luanetfilter

* remove LUADATA_OPT_SKB from luaxtables (it's broken)

fix struct sockaddr version check

* sa_data_min field was introduced on v5.15.150, removed on v5.16 and
  reintroduced on v6.1.80

fix struct sockaddr version check

* sa_data_min field was introduced on v5.15.150, removed on v5.16 and
  reintroduced on v6.1.80

adjust copyright year