Implement support for large enums (c++ generator)
Implement support for large enums (c++ generator)

Currently, the C++ generator generates one else-if branch for each enum
field. This causes troubles with compilers. MSVC for example limits the
number of branches to 128.

Also, conditionally checking enum fields step-by-step is at some point
slower than looking it up in a hashmap.

quicktype/quicktype,quicktype/quicktype,quicktype/quicktype,quicktype/quicktype,quicktype/quicktype