Changes to the code style guideline

Hi,

today I switched from FreeBSD's indent to GNU indent and found they handle things differently (even when using GNU indent with -orig option). Therefore I made the following adjustments to the coding style guideline:

- Length of code line is extended to 100 columns, but comments should still wrap at 79.
- Case labels are not indented at all (GNU indent does not support those 'half tab indents').
- C++ comments will be handled more relaxed.

The Developer's Guide has been updated accordingly and provides sample indent profile settings.

Regards,
Markus