- rename `edit_new` as `qe_new_window`
- report error in `qe_new_buffer` and `qe_new_window` upon failure
- rename `qe_find_buffer_file` as `qe_find_buffer_filename`
- rename `read_charset` as `qe_parse_charset`
- reset yank buffer references in `eb_clear()`
- make `qe_init()` return error code and abort upon error