Hello,

This is my first time contributing a patch, so hopefully I did everything 
right. The patch adds two packages for Lua 5.1; the new packages are based on 
the existing Lua 5.2 packages. The reason we need separate packages for Lua 
5.1 and 5.2 is because Lua is not backwards compatible between releases: there 
is no guarantee that code working on 5.1 will work on 5.2 or vice-versa (even 
though it probably will, we don't want to rely on probably). These two 
packages will be needed by the Neovim package later.