CDB: Fix step into, improve multithread dumping, exception logging
Use new call syntax of 6.11. for dumper call loading. Execute Dumpers in a single thread (current) if at all possible (not in some WaitFor or artificial break thread). Show one more frame in threads view if it is FastCallReturn. Fix step into (ignore one event), log some more exceptions. Generally log exceptions to the debugger windows to be able to see stuff like DLL missing, etc.