Revert "Added basic frame for new target 'creativision'."

This reverts commit 8e6b8dd0afed52c1963ea29c4921157693463cbe.
add SER_ERR_NOT_OPEN status code
add SER_BAUD_56_875
add serial driver for Atari, still contains much debug code
remove debug code
remove old (static) serial driver boilerplate
small optimzation (found by Greg King)
Merge pull request #64 from groessler/something_to_pull

Serial driver for Atari