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.

Avoid mix-up with array_index member
Co-Authored-By: Niels Lohmann <niels.lohmann@gmail.com>

Update README.md : add a FAQ about memory release

Fix typo in examples

README: Fix string representation of `dump`ed `json`

Fixes gcc48 warning:

declaration of ‘array_index’ shadows a member of 'this' [-Wshadow]

As is it's confusing and inconsistent with the indented form right below. The backslash escapes make it confusing.

Some typos

Readme: Updated links to hunter repo & docs

Fix link to parse function in README

hunter was recently passed over to a new maintainer, this is why the github url & the link to the documentation have changed.

Adds instruction for using Build2's package manager

(proper naming suggested by `build2`'s author)

I created a `nlohmann-json` package for `build2` (https://build2.org) that have been published on the central public repository https://cppget.org : https://cppget.org/nlohmann-json (at the moment you can see that there is only one version: 3.7.3).

The repository of the package code is there: https://github.com/build2-packaging/nlohmann-json and is owned by the build2 community now. (with build2 you can use either a repository like cppget.org or a git repository so both are useful to users for different use cases).

This patch just add the basic information as to how to use this library with build2.

Update README.md