Implement a --backtrace-all mode for winedbg

[Eric Pouech]

I'm not sure I understand the purpose of the --backtrace-all.
There's no way you can ensure a complete synchro between all threads & 
processes to get a global picture of the whole system, so the option is 
likely not very useful (except for the threads which are in a wait 
operation), but you will miss some other information for that (ie an 
event (entering/leaving CS...) tracker tool would be better).
More over, I don't like either adding options to winedbg. So, I'd prefer 
adding an option to actually process the commands from a file (or even a 
string from command line) would be better.
And, finally, you leak the handle for the snapshot.
A+