* Bulk replaced tabs with spaces
* Bulk removed trailing whitespace from lines
* Replaced c-style comments with c++-style comments in file banners
* Replace nested namespace definitions with single concise definitions (C++17), this keeps the indentation more manageable
* Cleanup ordering and spacing of include directives
* Bulk renaming of header file extensions from '.h' to '.hpp'.
* Update CODING-STYLE.md
* Update target_compile_features from cxx_std_11 to cxx_std_20.
* Refresh .clang-format file. Still needs a lot of tweaking.
QRcode_clearCache has been deprecated in libqrencode 4.0. In previous versions,
it was only necessary to help debug memory leaks. So it should be harmless
to remove this call.
Jaye Evins