I *think* this comes from installing a recent .tar.gz over a fairly old
source tree; strerror.c moved and split strerror() into two pieces, one
of which is named __strerror() (for the benefit of pipe.c, as I recall).
It might help to completely delete the libc heirarchy and reinstall, if
that's the case.  You can also look for files named "pipe.c" and "strerror.c"
and delete the older ones (one disadvantage of make compiling everything in
a directory; you have to actively remove outdated files).

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