Dietmar.
I think the segfault is not coming from oppenssh. The segfault happens in pthread library which is part of the glibc. (You also have seen crashes in other apps as well).
I tried to recompile (native and cross) the libc from debian, but failed in many different ways before I gave up.
It would be very helpful, if you could recompile the default libc on the debian system and see if the crash goes away with different compiler flags. (If you go this route, let me know I can hint you into the right direction with some links)
Tom