[PATCH] Extend the test for "svnadmin hotcopy" copying symlinks

In testing for back-port to 1.6.x, I wanted a more thorough test, so
here it is.

[[[
Extend the test for "svnadmin hotcopy" copying symlinks. Ensure that the
result is a symlink and not just a copy of the original symlink's target.
Ensure that the new symlinks has the same target as the old one. Check
symlinks that point to targets in the source repository and outside it, of
types file, dir and missing, with both absolute and relative paths.

There was no problem; I just wanted to be sure it would copy all of these
combinations properly before approving for back-port.

* subversion/tests/cmdline/svnadmin_tests.py
  (hotcopy_symlink): Extend the test as above.
]]]

- Julian