GOOD NEWS!!!
The previously reported bug (undefined reference to `__st??___ex_table') in
kernel version 2.1.7 has gone.
After re-re-re-re-re-re-install libc-5.4.10 (what I've done just before
the errornous compile, also) and removing all suspicious old stuff and
recompiling v2.1.7: IT WORKS!
And (much more better): In this kernel the mounting of my SCSI-CDROM
works also, which was impossible in 2.1.6 (kernel hangs).
Until now, all runs fine!
KEEP HACKING!
meino