Adding upstream version 0.17.0.upstream/0.17.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+= Usage of {cpp} within RNP
+
+This is a provisional document reflecting the recent conversion from C
+to {cpp}. It should be revisited as experience with using {cpp} within RNP
+codebase increases.
+
+== Encouraged Features
+
+These are features which seem broadly useful, their downsides are minimal
+and well understood.
+
+ - STL types std::vector, std::string, std::unique_ptr, std::map
+
+ - RAII techniques (destructors, smart pointers) to minimize use of
+   goto to handle cleanup.
+
+ - Value types, that is to say types which simply encapsulate some
+   data.
+
+ - std::function or virtual functions to replace function pointers.
+
+ - Prefer virtual functions only on "interface" classes (with no data),
+   and derive only one level of classes from this interface class.
+
+ - Anonymous namespaces are an alternative to `static` functions.
+
+== Questionable Features
+
+These are features that may be useful in certain situations, but should
+be used carefully.
+
+ - Exceptions. While convenient, they do have a non-zero cost in runtime
+   and binary size.
+
+== Forbidden Features
+
+These are {cpp} features that simply should be avoided, at least until a
+very clear use case for them has been identified and no other approach
+suffices.
+
+ - RTTI. This has a significant runtime cost and usually there are
+   better alternatives.
+
+ - Multiple inheritance. This leads to many confusing and problematic
+   scenarios.
+
+ - Template metaprogramming. If you have a problem, and you think
+   template metaprogramming will solve it, now you have two problems,
+   and one of them is incomprehensible.