This function was broken in Linux libraries up to and including libc 5.0.9;
there the `needle' and `haystack' arguments were interchanged, and a pointer
to the end of the first occurrence of needle was returned. Since libc
5.0.9 is still widely used, this is a dangerous function to use.
Both old and new libc's have the bug that if needle is empty
haystack-1 (instead of haystack) is returned. And glibc 2.0
makes it worse, and returns a pointer to the last byte of `haystack'. This is
fixed in glibc 2.1.