Warn about avserver being broken.

Also remove mentions of it from other avtools' manuals.

doc/avconv.texi

@@ -256,7 +256,7 @@ Set the number of video frames to record. This is an alias for @code{-frames:v}.
 @item -r[:@var{stream_specifier}] @var{fps} (@emph{input/output,per-stream})
 Set frame rate (Hz value, fraction or abbreviation), (default = 25).
 @item -s[:@var{stream_specifier}] @var{size} (@emph{input/output,per-stream})
-Set frame size. The format is @samp{wxh} (avserver default = 160x128, avconv default = same as source).
+Set frame size. The format is @samp{wxh} (default - same as source).
 The following abbreviations are recognized:
 @table @samp
 @item sqcif
@@ -1025,7 +1025,7 @@ the input file in reverse order.
 @settitle avconv video converter
 
 @c man begin SEEALSO
-avplay(1), avprobe(1), avserver(1) and the Libav HTML documentation
+avplay(1), avprobe(1) and the Libav HTML documentation
 @c man end
 
 @c man begin AUTHORS

doc/avplay.texi

@@ -172,7 +172,7 @@ Seek to percentage in file corresponding to fraction of width.
 @settitle AVplay media player
 
 @c man begin SEEALSO
-avconv(1), avprobe(1), avserver(1) and the Libav HTML documentation
+avconv(1), avprobe(1) and the Libav HTML documentation
 @c man end
 
 @c man begin AUTHORS

doc/avprobe.texi

@@ -122,7 +122,7 @@ with name "STREAM".
 @settitle avprobe media prober
 
 @c man begin SEEALSO
-avconv(1), avplay(1), avserver(1) and the Libav HTML documentation
+avconv(1), avplay(1) and the Libav HTML documentation
 @c man end
 
 @c man begin AUTHORS

doc/avserver.texi

@@ -22,6 +22,10 @@ avserver [options]
 @chapter Description
 @c man begin DESCRIPTION
 
+WARNING: avserver is unmaintained, largely broken and in need of a
+complete rewrite. It probably won't work for you. Use at your own
+risk.
+
 avserver is a streaming server for both audio and video. It supports
 several live feeds, streaming from files and time shifting on live feeds
 (you can seek to positions in the past on each live feed, provided you