Use svn_hash_gets and svn_hash_sets.

This converts the one instance of APR_HASH_KEY_STRING left in the parts of the
code that were subjected to the search-and-replace (subversion/**/*.c except
subversion/tests/), which is not #ifdef'd away.  I'm not sure why the
search-and-replace didn't match it.

* subversion/libsvn_repos/rev_hunt.c
  (is_path_in_hash): s/apr_hash_get/svn_hash_gets/


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1460178 13f79535-47bb-0310-9956-ffa450edef68