Unify some duplicated code before things get out of sync:
* subversion/include/svn_types.h, subversion/libsvn_subr/validate.c (svn_mime_type_is_binary): New function. (svn_mime_type_validate): Renamed from svn_validate_mime_type, so we have a consistent prefix for mime-type stuff now. All callers changed.
* subversion/clients/cmdline/feedback.c (notify): Just call svn_mime_type_is_binary, instead of doing it by hand.
* subversion/libsvn_wc/questions.c (svn_wc_has_binary_prop): Same, and users may apply in person for a refund of the cycles wasted this way.
* subversion/mod_dav_svn/liveprops.c (dav_svn_namespace_uris, DAV_SVN_NAMESPACE_URI, SVN_RO_SVN_PROP, SVN_RW_SVN_PROP, dav_svn_props, dav_svn_insert_prop): Use new namespaces for dav-ish properties. (DAV_SVN_NAMESPACE_URI_OLD, SVN_RO_SVN_OLD_PROP, SVN_RW_SVN_OLD_PROP): Were DAV_SVN_NAMESPACE_URI, SVN_RO_SVN_PROP, and SVN_RW_SVN_PROP, respectively.
* subversion/libsvn_ra_dav/commit.c (log_message_prop, do_proppatch): Use new property namespace(s) when the time is Right.
* subversion/mod_dav_svn/deadprops.c (dav_svn_db_define_namespaces, get_repos_propname, dav_svn_db_output_value, get_name, save_value): Use new property namespaces.
* subversion/include/svn_dav.h (SVN_FEATURE_USE_OLD_NAMESPACES): New #define for helping us find and remove support for old namespaces in the future.
* subversion/libsvn_ra_dav/ra_dav.h (SVN_RA_DAV__PROP_BASELINE_RELPATH_OLD, ELEM_baseline_relpath_old): Wrap with new #define so we can more easily find and remove this code in the future.
* subversion/libsvn_ra_dav/props.c (elem_definitions, neon_descriptions, starting_props, validate_element, svn_ra_dav__get_baseline_info): Wrap use of old namespaces with new #define.
* subversion/libsvn_ra_dav/fetch.c (svn_ra_dav__get_dir, add_props): Wrap use of old namespaces with new #define. (filter_props): Wrap use of old namespaces with new #define. Also, pass final NULL to apr_pstrcat.