Support environments that cannot use STL

[henrygab]

The headers use vector<> and other STL structures.

STL is not available on all IOT compilation environments, and some environments prohibit exceptions (which are required by the STL).

Please consider providing code that can be used (declares an API) that does not rely upon STL. Otherwise, there will be many implementations, each of which will have distinct bugs (and fail in unusual ways), which would require the client code to work around.