Bugfix: Invalid content count in FSS Basic List.

Bugfix: Invalid content count in FSS Basic List.

When F_none_eos or F_none_stop is returned, the content ends up having an additional size than the actual size.
This is happening because found->used++ is incremented immediately before returning.
When either F_none_eos or F_none_stop is returned, the content is not to be incremented.
Only the caller should know when to assume this is a proper ending representing the content end.

The macro private_macro_fl_fss_content_return_on_overflow_delimited() is only used in one place so remove it.

Make sure to initialize the content for all content read functions to ensure the content count is consistent.