Cocoa: fix single punctuation input via CJK input method

2d05d3bd2815c220474b3c07bf3f2ef7417d3070 was not correct.

On OS X, when user uses CJK input method, only types single punctuation,
it was converted to CJK ones, and not showed in composing text.

Task-number: QTBUG-35700
Change-Id: I2d1063d2f837d075929dc5ebb5722fdefc6ee0f6
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>