Canonicalize the authz file config in mod_authz_svn.

* subversion/mod_authz_svn/mod_authz_svn.c
  (canonicalize_access_file): New function.
  (AuthzSVNAccessFile_cmd, AuthzSVNReposRelativeAccessFile_cmd): Use
    canonicalize_access_file().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1429121 13f79535-47bb-0310-9956-ffa450edef68