* Add versioned inline namespace
Add a versioned inline namespace to prevent ABI issues when linking code
using multiple library versions.
* Add namespace macros
* Encode ABI information in inline namespace
Add _diag suffix to inline namespace if JSON_DIAGNOSTICS is enabled, and
_ldvcmp suffix if JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON is enabled.
* Move ABI-affecting macros into abi_macros.hpp
* Move std_fs namespace definition into std_fs.hpp
* Remove std_fs namespace from unit test
* Format more files in tests directory
* Add unit tests
* Update documentation
* Fix GDB pretty printer
* fixup! Add namespace macros
* Derive ABI prefix from NLOHMANN_JSON_VERSION_*
* Make exception context optional
Change exception context parameter to pointer and replace context with
nullptr where appropriate.
* Support escaping other string types
* Add string concatenation function
Add variadic concat() function for concatenating char *, char, and
string types.
* Replace string concatenations using + with concat()
* Template json_pointer on string type
Change json_pointer from being templated on basic_json to being
templated on string type.
* Add unit test for #3388Closes#3388.
* Fix regression test for #2958
* Add backwards compatibility with json_pointer<basic_json>
* Update json_pointer docs
* Allow comparing different json_pointers
* Update version numbers
