Treat symlinks better in $ORIGIN determination in ld.so

Treat symlinks better in $ORIGIN determination in ld.so

Now symlinking an executable away from the rest of its installation
tree no longer prevents it from finding the libraries. This matches
the behavior of other OS linkers. Prompted by a behavior change in
lang/ghc test suite.

Swapped the order of dirname/realpath in _dl_origin_path.

Added some regress tests that pass and then bin3 that fails without
this change and reflects the behavior needd for lang/ghc.

Suggestion by semarie@, OK deraadt@