Fix GCC compiler warnings

Fix Clang compiler warnings

Update doctest to 2.3.7

make CMake's version config file architecture-independent

fix warnings in serializer.hpp for VS2019

Fix C26451 warnnings in to_chars.hpp

Add binary type support to all binary file formats, as well as an internally represented binary type

Add binary type support to all binary file formats, as well as an internally represented binary type

catch exceptions for json_pointer : ..../+99

Templatize basic_json constructor from json_ref

Replace deprecated std::is_pod

Modify the document about operator==

Added wsjcpp.yml

Fixes #1971 (memory leak in basic_json::push_back)

appveyor.yml: Compile and test with latest version for __cplusplus ma…

According to [1] the C++ macro __cplusplus has always the value 199711L
even if you enable later version of C++ support via /std.

Use one job with /Zc:__cplusplus defined so that we know that it
compiles.

[1]: https://docs.microsoft.com/en-us/cpp/build/reference/zc-cplusplus?view=vs-2019

Rename argument array_index to array_indx in json_pointer methods

fix error 'setw' is not a member of 'std' in Wandbox example

Update LICENSE.MIT

PR for #2006 to test in AppVeyor.