Debugger: Fixed and improved: Stop/Kill GDB when debugger stops

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43837 4005530d-fff6-0310-9dd1-cebe43e6787f
Debugger: Avoid error state, if GDB is killed.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43838 4005530d-fff6-0310-9dd1-cebe43e6787f