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

Fix -Wundef warnings when building liblua

We need to define the LUA_FLOAT_INT64 macro even if we don't use it (copied
from stand/luaconf.h). While touching luaconf.h.dist also sync it with the
the 5.3.5 release version (matches the one in lib/liblua).

Reviewed By: kevans
Differential Revision: https://reviews.freebsd.org/D25977

flua: don't allow dlopen, et al., for bootstrap flua

There are some logistics issues that need to be sorted out here before we
can actually allow this to work.

flua: support "require" for binary objects in the base system

Export symbols from flua, and enable dlopen.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26059

flua: initial support for "require" in the base system

Use /usr not /usr/local for base system components.

Use /usr/lib/flua and /usr/share/flua (not lua) for consistency and to
avoid the possibility that other software accidentally finds our base
system modules.

Also drop the version from the path, as flua represents an unspecified
lua version that corresponds to the FreeBSD version it comes with.

LUA_USE_DLOPEN is not yet enabled because some additional changes are
needed wrt symbol visibility.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D24605

liblua: ensure that "require" will fail in bootstrap flua

We do not want to support bootstrapping lua modules, so ensure that
require will fail by providing a nonexistent path.

Reviewed by: kevans
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D24610

Add an internal liblua and use it in flua.

The new liblua will be used in a forthcoming import of kyua.

Reviewed by: kevans
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24090