Allow svn_ra_get_file_revs2() and svn_repos_get_file_revs2() to report file
revisions backwards. This to allow optimizing 'svn blame' in a future
Subversion release without having to wait for yet another server upgrade
to support this new feature.

* subversion/include/svn_ra.h
  (svn_ra_get_file_revs2): Update documentation.

* subversion/include/svn_repos.h
  (svn_repos_get_file_revs2): Update documentation.

* subversion/libsvn_repos/rev_hunt.c
  (svn_repos_get_file_revs2): Update comment. Detect reversed arguments,
     which would originally just return an error or no revisions..
     and in that case reverse the revision array before walking it.

* subversion/tests/libsvn_repos/repos-test.c
  (test_get_file_revs): Extend test to also walk the revisions backwards.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1445973 13f79535-47bb-0310-9956-ffa450edef68
* subversion/libsvn_subr/sorts.c
  (svn_sort__array_reverse): Replace a debug-only assertion with an
    implementation for non pointer sized array items, which I hope
    we never need. But everything is better than silent memory corruption
    in release mode.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1445980 13f79535-47bb-0310-9956-ffa450edef68