Adding the `->` operator to the structure pointer part

[noah1510]

The section on pointer operations is missing the -> operator which is used to access values that are part of a pointer to a class/struct.

In addition to that there is no mention of how to either use/define classes and templates. With the current way the Structure section is written it has nothing to do with C++ just plain C (nothing wrong with that except for being misleading/incomplete). However this is in part covered by #623.