try to cache the build dependencies
Remove the deprecation notice from the old Lua interface

Fixes #5332.  The impending deprecation should probably still be
mentioned in the release notes.
Merge pull request #5344 from obrakmann/remove-lua-deprecation-notice

Remove the deprecation notice from the old Lua interface
Merge pull request #5335 from Mailaender/travis-cache

Try to cache the build dependencies for Travis CI