devel/rttr: Fix build on 14- / modern Clang

- the bundled rapidjson doesn't build on 14- because of changes
  in the STL; use the version from ports instead which has the
  changes needed already.
- the chaiscript examples don't build with modern Clang on 14-,
  and the examples are explicitly C++14 -- but still don't work

Replace the bundled rapidjson and chaiscripts with the
regular ports versions. There has been some work in git
on both rttr and chaiscript, but neither has a newer
release that might be pulled in, so we'll stick to messy
patching of rttr instead.