lua: reduce diffs between luaconf.h copies

Upstream luaconf.h is contrib/lua/src/luaconf.h.dist, while userland lua
and loader lua have copies in lib/liblua/luaconf.h and
stand/liblua/luaconf.h.

Adjust whitespace, VCS tags, etc. to match upstream's version, for ease
of comparison.

Reviewed By: imp
Sponsored By: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D38206