LLI and the ORC C-bindings each have their own stack, but they have a lot of overlapping functionality. They should almost certainly share a single stack, which could also be made directly available to LLVM clients who want to use it.
The unified stack might also be shared with the Kaleidoscope tutorials.
LLJIT (git# 9f1c2395ce1, svn r335670) is a reasonable contender for a solution to this. It has replaced OrcLazyJIT for lli, but we still need to move the C API bindings over (or better yet write some new ones) before we close this.