Use pointers to incomplete struct types. If an argument of a not suitable
type is passed to a function of any string collection,
C compiler will warn:
warning: passing argument 1 of <func> from incompatible pointer type
C++ compiler will raise an error, for example:
error: cannot convert 'cef_string_list_t' ... to 'cef_string_multimap_t'
With the previously used `void*` pointer types, such errors in a code were not
diagnosed.
Marshall Greenblatt
Sergey Markelov