uhd: Symbolic block names now match the standard naming
blocks: fix for qa_python_message_passing and new system port
uhd: Fixed "reducing chan number" bug

In some cases, there could be an error when reducing the number
of chans for UHD device in GRC (e.g. going from 2 chans to 1).
This adds another check which will alert the user.
Merge branch 'maint'
Merge branch 'master' into next