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.