exceptions: optionally enforce c++ standards

[d-a-v]

#6312 restored "arduino new" 's right to return nullptr

This PR optionally allows to enforce C++ standards by making new call abort in case of OOM.

It also introduces an optional allocator to allow a clean behaviour in case of oom.

check maintainers' effort to document new without exceptions .

[earlephilhower]

LGTM. Good job summarizing the infinite loop of the new discussion.

[d-a-v]

Benefits brought by the new allocator: example output

[TD-er]

infinite loop of the new discussion.

That's a true statement in itself :)

[d-a-v]

Thanks @earlephilhower for reminding #4639 (allowing the last commit)