s390x: glibc widestring algorithms broken
Description of problem:
Several wide-string functions from glibc are broken und qemu user emulation.
Affected are at least: `wcsbrk()`, `wcsspn()` and `wcscspn()`. All of these are implemented in optimized assembler in glibc.

Unfortunately I don't have access to the real hardware to check the behavior there. But it would probably been detected by now.
Also I don't know which instructions exactly don't work, as I don't have any knowledge about s390x assembler.
Steps to reproduce:
1. Compile the test program above
2. Run the program
3. Output is `0`, should be `1`.