Remove SIGEMT completely.

It was a remnant of an earlier version of the code written on OSX.
Nobody should write code on OSX first. But hey, bed coding is comfy.

(Also nobody reads those anymore. If you're there, though, hi!)
Fix fancy_backtrace for Win64 again

It was broken in the capture / formatting separation thingy.
Apparently SymInitialize needs to be called pretty much everywhere!

Maybe we should call SymInitialize only once at the load of the DLL..
but then it wouldn't work on DLLs loaded later.