Redesign and implement "fetch repository info".

Introduce independent functions, replacing the info struct.  Remove hooks
support for now; it could be added by reusing hooks.c:check_hook_cmd().

* subversion/include/svn_repos.h
  (svn_repos_capabilities): Point to this function from the "if you add a new
    capability" comment.
  (svn_repos_info_format): New function.
  (svn_repos_info, svn_repos_info_t, svn_repos_info_dup):
    Delete declarations (which have never been implemented)..

* subversion/libsvn_repos/repos.c
  (svn_repos_capabilities): Implement.
  (svn_repos_info_format): Implement.
  (svn_repos_info, svn_repos_info_t, svn_repos_info_dup):
    Delete stub definitions.

* subversion/tests/libsvn_repos/repos-test.c
  (svn_hash.h, svn_version.h): Include.
  (test_repos_info): New function.
  (test_funcs): Run it.

* subversion/libsvn_repos/repos.h
  (SVN_REPOS__FORMAT_NUMBER, SVN_REPOS__FORMAT_NUMBER_1_4):
    Juggle macros a little to ensure that svn_repos_info_format() would trip
    if we increment the format number without changing the "format number to
    version number" logic therein.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1465147 13f79535-47bb-0310-9956-ffa450edef68