Update: get the level_3 / programs working after major file / directory changes

Update: get the level_3 / programs working after major file / directory changes

This required making some fixes in the files related code.
This puts the UTF-8 file (utf_file) project notably behind an additional work is necessary to get that working correctly as well as having it be consistent with f_file.

I've decided that when written pointer is 0, then the caller is requesting to not get back the written size.
I am very likely going to do similar behavior with null pointers in other uses, which will help further simplify the design.

Other minor changes.
Of particular note is moving flags into the f_file structure.
This was effectively how the pre-file redesign worked, but it uses flags now instead of the "r", "rw", "a", etc.. string modes used by fopen.
Make sure an append flag is available.