Add Lua script to l3kernel and adjust main scripts to fit

This allows unpacking l3kernel into a local directory, so the tests for
everything else do not depend on the current distribution/local installation.

Note that:
 - make check is not implemented as it depends on the outcome of dicussions
   about tests in general
 - make ctan/localinstall do not currently handle l3doc.ist
 - make unpack uses only 'local' files whereas make doc and make check
   currently use local files first then the distro tree
 - Some efficiencies can probably be made with unpacking l3kernel


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4791 de43f980-851b-0410-b2f7-c40aca1f87e0
Set SVN property on new .lua file


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4792 de43f980-851b-0410-b2f7-c40aca1f87e0