Remove the ability of svn_repos_authz_read2() to handle repos-relative URLs.

This cleans up a case where it was impossible to canonicalize the paths
being passed into it and also ends up removing the need to pass repos_root
into it.  If callers want to support repos-relative URLs then they should
resolve them into absolute file URLs and canonicalize them prior to calling
svn_repos_authz_read2().

* subversion/include/svn_repos.h
  (svn_repos_authz_read2): Remove repos_root argument and adjust documentation
    to account for no longer accepting repos-root URLs.  Also change "a file"
    in the documented formats for path to a dirent to be more precise.

* subversion/libsvn_repos/authz.c
  (authz_retrieve_config_repo, svn_repos__authz_read, svn_repos_authz_read2):
     Remove repos_root parameter and support for repos-relative URLs in path.

* subversion/libsvn_repos/deprecated.c
  (svn_repos_authz_read): Adjust call of svn_repos__authz_read().

* subversion/libsvn_repos/repos.h
  (svn_repos_authz_read): Adjust declaration and documentation to match the
    removal of repos_root and support for repos-relative URLs.

* subversion/mod_authz_svn/mod_authz_svn.c
  (canonicalize_access_file): Adjust comment about why we are not canonicalizing
    here.
  (get_access_conf): When access_file is a repos-relative URL resolve and
    canonicalize it before calling svn_repos_authz_read2().

* subversion/svnserve/serve.c
  (canonicalize_access_file): Change access_file to an arginout and return
    an svn_error_t so that we can resolve and canonicalize repos-relative
    urls.
  (load_authz_config): Adjust calls to canonicalize_access_file() due to
    above changes.

* subversion/tests/libsvn_repos/repos-test.c
  (in_repo_authz, in_repo_groups_authz): Remove repos-relative URL tests
    and convert still needed tests that were using repos-relative URls to
    absolute URLs.

* tools/server-side/svnauthz.c
  (get_authz): Fix call to svn_repos_authz_read2() to match above changes.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1463374 13f79535-47bb-0310-9956-ffa450edef68