Reverting of #2004 and #1457 (Configure.pl --cxx)

[Vasily Chekalkin]

Hello.

We used to support --cxx option in Configure.pl which was removed in
#2004 and #1457 trac tickets. I think it was a mistake. We have to
provide way of specifying some kind of functional C++ compiler for C++
extensions. For example LLVM bindings/jit. I'm slightly blocked on
jit_prototype from testing purpose because LLMV C API doesn't provide
enough functionality comparing C++ API.

-- 
Bacek