doc: remove references to external documents

Fix a few warnings generated when creating the manuals.

Our current doc generation toolchain does not allow to reference external
documents.

doc/avtools-common-opts.texi

@@ -152,11 +152,12 @@ directory.
 This file can be useful for bug reports.
 It also implies @code{-loglevel verbose}.
 
-Setting the environment variable @code{FFREPORT} to any value has the same
-effect. If the value is a ':'-separated key=value sequence, these options
-will affect the report; options values must be
-@ref{quoting_and_escaping, escaped} if they contain special characters or
-the options delimiter ':'. The following option is recognized:
+Setting the environment variable @code{FFREPORT} to any value has the
+same effect. If the value is a ':'-separated key=value sequence, these
+options will affect the report; options values must be escaped if they
+contain special characters or the options delimiter ':' (see the
+``Quoting and escaping'' section in the ffmpeg-utils manual). The
+following option is recognized:
 @table @option
 @item file
 set the file name to use for the report; @code{%p} is expanded to the name

doc/ffmpeg-devices.texi

@@ -23,8 +23,8 @@ libavdevice library.
 The libavdevice library provides the same interface as
 libavformat. Namely, an input device is considered like a demuxer, and
 an output device like a muxer, and the interface and generic device
-options are the same provided by libavformat (see the @ref{FFmpeg
-formats} manual page).
+options are the same provided by libavformat (see the ffmpeg-formats
+manual).
 
 In addition each input or output device may support so-called private
 options, which are specific for that component.

doc/ffmpeg.texi

@@ -938,7 +938,8 @@ ffmpeg -i input.mpg -timecode 01:02:03.04 -r 30000/1001 -s ntsc output.mpg
 Define a complex filter graph, i.e. one with arbitrary number of inputs and/or
 outputs. For simple graphs -- those with one input and one output of the same
 type -- see the @option{-filter} options. @var{filtergraph} is a description of
-the filter graph, as described in @ref{Filtergraph syntax}.
+the filter graph, as described in the ``Filtergraph syntax'' section of the
+ffmpeg-filters manual.
 
 Input link labels must refer to input streams using the
 @code{[file_index:stream_specifier]} syntax (i.e. the same as @option{-map}

doc/filters.texi

@@ -240,8 +240,8 @@ And finally inserted in a filtergraph like:
 drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
 @end example
 
-See the @ref{quoting_and_escaping, Quoting and escaping} section for
-more information about the escaping and quoting rules adopted by
+See the ``Quoting and escaping'' section in the ffmpeg-utils manual
+for more information about the escaping and quoting rules adopted by
 FFmpeg.
 
 @c man end FILTERGRAPH DESCRIPTION
@@ -5371,12 +5371,12 @@ starting from this seek point, the parameter is evaluated with
 postfix. Default value is "0".
 
 @item streams, s
-Specifies the streams to read. Several streams can be specified, separated
-by "+". The source will then have as many outputs, in the same order. The
-syntax is explained in the @ref{Stream specifiers} chapter. Two special
-names, "dv" and "da" specify respectively the default (best suited) video
-and audio stream. Default is "dv", or "da" if the filter is called as
-"amovie".
+Specifies the streams to read. Several streams can be specified,
+separated by "+". The source will then have as many outputs, in the
+same order. The syntax is explained in the ``Stream specifiers''
+section in the ffmpeg manual. Two special names, "dv" and "da" specify
+respectively the default (best suited) video and audio stream. Default
+is "dv", or "da" if the filter is called as "amovie".
 
 @item stream_index, si
 Specifies the index of the video stream to read. If the value is -1,