Move list of open message queues to task group. Now message queues opened by...

Move list of open message queues to task group.  Now message queues opened by members of the group will be closed when the last member of the group exits.

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5609 42af7a65-404d-4744-a932-0658087f49c3