POSIX: Your queue depth may be too large

[aFunnyBit]

Update documentation to show Posix fix:

Edit /etc/sysctl.conf and add the lines:

	# Increase message queue
	fs.mqueue.msg_max = 256

Or

Edit as root /proc/sys/fs/mqueue/msg_max is set to 256 or some value appropriate.

root# echo 256 > /proc/sys/fs/mqueue/msg_max

[skliper]

Due to refactoring repos, added comment at https://github.com/nasa/cFS/blob/rc-6.6.0a/README.md

Will get pushed to master once bundle completes testing.