notably, test normal + single + generated + Lua 5.3.5 only once,
then only run the runtime_test and compile_test for normal for all other permutations to help increase text matrix throughput
add new shared_ptr differentiation mechanism that persists between DLLs (fixes#661)
change valid Lua version to handle Lua 5.4.0-work1 (fixes#649)
remove upper limit on MSVC version: they're not fixing it anytime soon (fixes#655)
add integer value for definition (fixes#651)
added variadic_results, to return a variable number of arguments to Lua
added variadic_results and as_results
added improved function examples (for multiple results and split overloading out)
added tests for variadics
added tests for C++17 utilities
added a forwarding header
added a specific `unsafe_function` header
added and improved documetation pages