Prepare to support Lua 5.4

[mpeterv]

lfs is already almost compatible with Lua 5.4, just need to fix an overly strict version check. With this patch lfs compiles and passes tests under Lua 5.4 work1, with and without -DNILINTABLE.

[coveralls]

Coverage remained the same at 80.144% when pulling 66482b9 on mpeterv:lua54-support into 1dfb8c4 on keplerproject:master.

[leokaplan]

Some libraries depend on lfs (in special busted). This would greatly ease the development in Lua 5.4

[hishamhm]

@leokaplan Thanks for the ping (and hi there, long time no see!) — it feels so bittersweet to merge a PR from @mpeterv. I will push a patch release containing this.

[hishamhm]

@leokaplan btw, have you tested that this is sufficient for supporting the latest rc of Lua 5.4?

[leokaplan]

I've compiled it with the latest release of 5.4 and ran with LUA_CPATH=./src/?.so lua5.4 tests/test.lua
then i've got:

LuaFileSystem 1.7.0
.............Ok!

So I think that everything is ok.
Also checked on the REPL, require'd it and played a little...

[leokaplan]

Being merged will it automatically change in luarocks?

[hishamhm]

No, I need to tag a new version number and push a release!