[C++] `<math>` builtins

[alexeyneu]

why log() goes as support.function.C99 ?

[FichteFoll]

(In case it's not easy to tell, this is about the C syntax.)
Please include the syntax/package the issue is about in the issue title.

[deathaxe]

Various syntaxes use support scopes to add special highlighting to functions which ship with standard libraries. If the question is why C++ uses C99, that's because C and C++ share various lines of code.