Make signals configurable

This allows for selecting the appropriate signals
and avoids conflicts with other tools that specific
signals i.e. profilers
Remove non-existing testcase from CMakeLists
Merge branch 'buildfix'
Improve as per bombela's suggestions, add test
Add default parameter to BACKWARD_SYSTEN_UNKNOWN signal handler
Merge pull request #7 from bastih/master

Allow for selection of signals thanks @bastih