Merge pull request #777 from cubbimew/nvi

dropping NVI from proto-rules due to no consensus on #768

CppCoreGuidelines.md

@@ -19427,7 +19427,6 @@ Alternatively, we will decide that no change is needed and delete the entry.
 * Never pass a pointer down the call stack
 * falling through a function bottom
 * Should there be guidelines to choose between polymorphisms? YES. classic (virtual functions, reference semantics) vs. Sean Parent style (value semantics, type-erased, kind of like `std::function`)  vs. CRTP/static? YES Perhaps even vs. tag dispatch?
-* Speaking of virtual functions, should non-virtual interface be promoted? YES. (public non-virtual `foo()` calling private/protected `do_foo()`)? Not a new thing, seeing as locales/streams use it, but it seems to be under-emphasized.
 * should virtual calls be banned from ctors/dtors in your guidelines? YES. A lot of people ban them, even though I think it's a big strength of C++ that they are ??? -preserving (D disappointed me so much when it went the Java way). WHAT WOULD BE A GOOD EXAMPLE?
 * Speaking of lambdas, what would weigh in on the decision between lambdas and (local?) classes in algorithm calls and other callback scenarios?
 * And speaking of `std::bind`, Stephen T. Lavavej criticizes it so much I'm starting to wonder if it is indeed going to fade away in future. Should lambdas be recommended instead?