project: add D demangling to LLVM

[Johan Engelen]

Hi all,
   There is the opportunity to add D demangling to LLVM, as you 
can see from this PR: https://reviews.llvm.org/rG7310403e3cdf
(the PR adds Rust demangling, clearly showing how D demangling 
could be added)

I think it will be a fun project to work on if you are interested 
in contributing to LLVM.
Impact estimate: D demangling capability in llvm-cxxfilt, 
libLLVM, and probably in the future also lldb.

cheers,
   Johan