Debugger: give item delegates a parent.

These delegates would otherwise be leaked. This is not a serious leak,
as a few (about 10) are created once and kept/used for the whole
lifetime of the application, but they do show up in leak-analysis tools.

Change-Id: I1e281f06f21ae828199078253ae5719668d26bbc
Reviewed-by: hjk <hjk121@nokiamail.com>