- fix notcurses_init unit test
- fix fn call name: `nplane_at_cursor_cell` → `ncplane_at_cursor_cell`.
- make LIBC_FILE & NC_FILE type aliases with doc comment.
- add lib module comment.
- improve direct-cursor example.
- fix full-text example and rename it to full-basics.
- remove _IO_FILE import and usage.
- create handy constructors for NcDirect & Notcurses.
(but can't implement destructors for copy types…).
- when possible substitute mutable pointers `*mut` for mutable references `&mut`
with associated lifetimes.
- new widgets module, starting with NcReader & NcReaderOptions constructors
