Regression: UPC++ reliance on RTTI

[Dan Bonachea]

Release 2019.9.0 did not rely on the C++ RTTI feature, and thus could be built and used with g++ -fno-rtti.

One of John's comments made me realize that recent development (by me) has introduced trivial dependencies on RTTI, breaking the ability to build with RTTI disabled (which some users might want to do, for at least perceived performance benefit).

[Dan Bonachea]

Remove hard dependence on RTTI from detail::typename_of<T>()

The utility now returns an emptry string when RTTI is unavailable.

Fixes issue #332

→ <<cset 9bf6d28991cb>>