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.