Log Message:
jsoncpp: updated to 1.9.0

1.9.0:
It's been ~2 years since the last release, so this has quite a few changes. Some \ 
highlights:
Build optimizations and updates. Now needs at least Meson 0.50.0, bot support \ 
for VS 2013 dropped in favor of VS 2017
Lots of bug fixes
Lots of enhancements
Lots of cleanup