add enum class default conversions

TIL about C++:

executing m[key()]=val(); for a std::map executes

First key() then val() with Clang

First val() then key() with GCC

#wat

- removed uncached input stream adapter; it was too slow anyway
- implemented a class binary_read which parses CBOR based on input
adapters
- in the CBOR parser, numbers are created via memcpy to avoid undefined
behavior

Properly pop diagnostics

The implementation is non-standard. Deprecation allows a simpler API in
the future without removing any features.

NaN values never compare equal to themselves or to other NaN values.

https://blog.travis-ci.com/2017-03-28-xcode-83-ga-is-here