Added tv25fps mode

Limits tv download to 25fps streams. Shorthand for "hlshd,tvvgood".
Utility is diminished because hlshd streams are likely to be missing
segments and thus generate errors. However, at lower quality levels
hvf streams will be preferred to hls streams, reducing risk of complete
failure due to missing segments in all hls streams.

get_iplayer

@@ -8159,6 +8159,7 @@ sub modelist {
 	}
 	# default on-demand tv
 	if ( $prog->{type} eq "tv" && $mlist =~ /tv/ ) {
+		$mlist = main::expand_list($mlist, 'tv25fps', 'hlshd,tvvgood');
 		$mlist = main::expand_list($mlist, 'tv', 'tvdefault');
 		$mlist = main::expand_list($mlist, 'tvdefault', 'tvbest');
 		$mlist = main::expand_list($mlist, 'tvbest', 'hvfhd,hlshd,tvbetter');