Feature: support f_string_constant_t as a way to pass "const char *" as a parameter.

Feature: support f_string_constant_t as a way to pass "const char *" as a parameter.

The parameter will have the return value and needs to be a pointer.
Passing "const char **", the "const" is applied to "char **", which is not what is wanted.
The desired logic is "(const char *) *", but that is not valid syntax.
To achieve this, "const char *" is turned into the typedef "f_string_constant_t".
This allows for "(const char *) *" to be used in the form of "f_string_constant_t *".

This is a special, exceptional, case and there are no plans to support an "array of" or any of the completeness practices.