[tex-live] Location of Lua binary extension modules

[Karl Berry]

    The downside is that it is not possible to e.g. install extension
    modules in a home directory.

I think people advanced enough to need that can be allowed to set
CLUAINPUTS as an environment variable.  That's what extra colons are
for, after all.  I wouldn't want to guess or prescribe any
platform-specific structure under TEXMFHOME, etc.

k