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 'upstream/master' into stm32f4_port
Revert "Merge remote-tracking branch 'upstream/master' into stm32f4_port"

This reverts commit 76d81d0f287671042ce36243998492800ca4b67e, reversing
changes made to 71b78db8d65ecf6871523b0491c75161e822eab5.