e6 issue 344 - changes and cleanup for proper handling of the different ...

...debug output choices

1. Modified config.in to really reflect the mutual exclusive options for debug output.
2. Modified debug.{c,h} to not generate superfluous code if no USART is uses and to compile without errors for controllers without USART.
3. Modified usart-config.sh to properly detect zero USARTs if a controller has none.
4. General cleanup of #include-directives.
5. Regenerated all profiles.

Manually tested debug w/usart, syslog and softuart. Compile autotest completes sucessfully w/ minor glitches (cpp-warnings) due to misconfigured profiles (beteigeuze).

This patch introduces a few new config symbols. Please regenerate your profiles by invoking menuconfig "General setup" once.

Review and comment please.
Uses two spaces instead of tabs as required by the wiki. Better use tabs here or re-indent whole file using spaces?