Remove (void) casts of ignored return values from mod_dav_svn, add
some extra handling for parameters that could be used when errors
are ignored.

* subversion/mod_dav_svn/liveprops.c
  (is_writable): Remove cast, only dereference non-NULL pointer.
  (dav_svn__insert_all_liveprops): Remove cast.

* subversion/mod_dav_svn/lock.c
  (unescape_xml): Remove cast, initialise buffer.

* subversion/mod_dav_svn/mod_dav_svn.c
  (merge_xml_in_filter): Remove cast.

* subversion/mod_dav_svn/util.c
  (dav_svn__final_flush_or_error): Remove cast, initialise length.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1464058 13f79535-47bb-0310-9956-ffa450edef68