Fixed wrong preprocessor symbol for attiny.
Updating handling of too long command line.

1. IOStream::Device::set_blocking/set_non_blocking set device state on.
2. IOStream::Device's refactored to use yield() instead of Power::sleep.
3. Non-blocking IOBuffer::putchar() has been removed.
4. Shell update to detect and handle too long command lines.
5. Ripple on Shell example sketches.