Fixes issue #33

Git bisect led me to 6509c8367f as the offending commit.

The "CC3000 SpiWrite acquire bus" message and
the "CC3000 DmaHandler release read spi bus" message
do not break debug mode, but they create enough debug loggin
as to overwhelm the serial bus.

The "CC3000 DmaHandler release write spi bus" actually breaks
debug mode. Removed as unimportant.
Merge remote-tracking branch 'origin/master' into stm32f4_port

Merge upstream bug fix.