Cpp/fix/#610

[j-cortial]

This PR fixes the sample code in #610 but is not a complete solution.
I would like to have your opinion on the fix before I go ahead and tackle raw string and character literals.

[j-cortial]

Now raw strings and (single-quoted) characters should be covered as well as standard double-quoted strings.

I did not use a scope beginning with keyword.other.unit.suffix since most suffixes (and especially string suffixes) have nothing to do with (physical) units.

The scope I used is keyword.other.suffix.literal.user-defined (to match the term used by https://en.cppreference.com/w/cpp/language/user_literal) and the refinement keyword.other.suffix.literal.user-defined.reserved when the suffix is reserved by the implementation (does not start with an underscore, such as the standard s and sv).

[jeff-hykin]

Thanks again! Published in v1.17.0