Notes on the C-to-C++ Conversion

libtransmission was written in C for fifteen years, so eliminating all Cisms is nearly impossible. Modernization patches are welcomed but it won't all happen overnight. tr_strdup() and constexpr wil exist side-by-side in the codebase for the forseeable future.
It's so tempting to refactor all the things! Please keep modernization patches reasonably focused so that they will be easy to review.
Prefer std:: tools over bespoke ones. For example, use std::vector instead of tr_ptrArray. Redundant bespoke code should be removed.
Consider ripple effects before adding C++ into public headers. Will it break C code that #includes that header?