Improve Opera 11 compatibility slightly
Support text input using MacOS’s option+char method

Some IMEs will stack end & start requests back to back. Code has been
added that forces the display to reset between new composition sessions,
rather than incorrectly interrupting the new composition session 0ms later
as would happen if the background task executes after the composition
start event.

One known edge case on Safari under MacOS is that if composition is ended by
pressing another text char, Safari reports a keypress event with the same value
as the last compositionend data, rather than the new key that was pressed.