Added C++11 and C++14 compatible code

[welshcoder]

I hope you find these changes helpful to enable older modern C++ compilers to use your code. Some embedded system compilers are at the C++11 or C++14 standard, so this is to enable the code to be used on those systems. I believe that the code will compile for C++17/C++20 as before (running it in CompilerExplorer suggest this to be the case).

[Reputeless]

Thanks for the suggestion! However, this library does not target C++14 for maintainability reason.