FIX Clone Config_LRU incl. objects in array

@hafriedlander Caused key confusions when using Config::nest()/unnest().
I've tried the `unserialize(serialize())` deep clone trick first, but that doesn't
preserve array keys properly, and is also much slower.

This should fix the Travis builds for sapphire. Please merge 3.1 into master after merging this PR, since it has the same issue.