Hi,
Long story short, the PSTL is pretty much ready to be shipped with LLVM. I did the integration between it and libc++, and it all worked last time I checked. I think the next step would be to change whatever LLVM scripts are used to create releases to also install the PSTL, which is the part I haven't had time to look into yet.
That being said, the PSTL will then default to using the Serial backend, which isn't very useful. We could decide to ship a different backend if we wanted, however I think what makes sense is to use a backend specific to the platform we're running on instead of adding a dependency to LLVM.
Louis