Improve troubleshoot and segmentation-fault documentation

[mostolog]

To debug and in order to help solving issues, users are requested to follow some steps, described at: http://www.rsyslog.com/doc/v8-stable/troubleshooting/troubleshoot.html

For someone with poor or none C skills, it seems quite hard/unclear to follow.

May this issue be a request to improve documentation to make an easy step-by-step troubleshooting guide, trying to get a "issue report" template.