Simple ordered_json that works on all supported compilers

Co-authored-by: Niels Lohmann <niels.lohmann@gmail.com>

(forgotten in previous commit!)

so that it can handle pair<const Key,...>

to extract the actual ObjectType::value_type
Still fails on older compilers (GCC <= 5.5)

This reverts commit 5fe3d392.

This is more comprehensive and the "my_workaround_fifo_map" wrapper does not allow to infer value type as required in this branch.

This reverts commit 064a9c92.

instead of hard-coding it for std::map's value_type

Improve parse_ubjson_fuzzer

Add input adapter tests

🏁 fix for MSVC (see https://github.com/nlohmann/json/pull/2178#issuecomment-640622532)

 Conflicts:
	doc/examples/swap__binary_t.link

Fix warnings