Update: recursive functions, fix 'const const', don't error on max recurse depth.

Update: recursive functions, fix 'const const', don't error on max recurse depth.

Rewrite the fl_directory_* recursive functions, simplifying their design.
Add a max recursion depth.
I have a toleration limit on the number of arguments in a function and this just reached a limit.
Given that many of the parameters can be logically grouped and are also are also passed to other functions, implement a new structure.
While this simply changes where the complexity/problems happen, this does alleviate the number of arguments concerns.

Fix an accidental 'const const' declaration.

Don't error on max recurse depth.
This should just stop recursing for that directory and not generated an error.