Originally had two seperate positions for reading/writing,
but this is inconsistent with the the posix standard, which
has a single position for reading and writing.
Also added proper handling of when the file is dirty, just
added an internal flag for this state.
Also moved the entry out of the file struct, and rearranged
some members to clean things up.
A rather involved upgrade for both files and directories, seek and
related functions are now completely supported:
- lfs_file_seek
- lfs_file_tell
- lfs_file_rewind
- lfs_file_size
- lfs_dir_seek
- lfs_dir_tell
- lfs_dir_rewind
This change also highlighted the concern that lfs_off_t is unsigned,
whereas off_t is traditionally signed. Unfortunately, lfs_off_t is
already used intensively through the codebase, so in focusing on
moving forward and avoiding getting bogged down by details, I'm going to
keep it as is and use the signed type lfs_soff_t where necessary.
