Incompatibility between sound and bubble notifications

When both bubble and sound notifications are enabled, evolution-indicator version 0.2.10-0ubuntu1 relies on the notification daemon to play the chime (through the sound-themed hint).

However the default notification daemon notify-osd doesn't support such a hint, nor the hint is specified in the Desktop Notification Specification:

http://www.galago-project.org/specs/notification/

As a result sound notification are automatically ignored if bubble notifications are on.