For a start, nobody uses UTF-32 for transmission/storage.
Then, we anyway have iconv() support in the subtitle support (where it
belongs IMHO), if you really wanted to use UTF-32.

Fix croppadd out of bounds write (we were padding 'paddleft+paddright' pixels on the right instead of 'paddright')

+ a few typo

(should probably be a per-instance lock instead though)