Update embedded jsoncpp from unk version to 0.10.6 + move libs to lib/ instead of...

Update embedded jsoncpp from unk version to 0.10.6 + move libs to lib/ instead of src/ (#5473)

* Update embedded jsoncpp from unk version to 0.10.6

0.10.6 is last release without c++11

* Make jsoncpp more compliant with its amalgamate

Jsoncpp cpp file should be upper, make the library like it does in amalgamate

* Reorganization: move minetest embedded libs outside of source tree to /lib

* Fix a dead grep in LINT