doc: remove inclusion of libav* documentation in tools

This shrinks the tool manuals to a manageable size. Relevant manuals are
referenced in the "See Also" chapter.

Overall documentation inclusion should still be possible through the use
of a conditional variable set during configuration time, if someone feels
the need for a huge-wall-of-text-fashioned manual.

doc/avtools-common-opts.texi

@@ -209,6 +209,3 @@ use @option{-option 0}/@option{-option 1}.
 
 Note2 old undocumented way of specifying per-stream AVOptions by prepending
 v/a/s to the options name is now obsolete and will be removed soon.
-
-@include avoptions_codec.texi
-@include avoptions_format.texi

doc/ffmpeg.texi

@@ -1276,19 +1276,6 @@ ffmpeg -i src.ext -lmax 21*QP2LAMBDA dst.ext
 @end itemize
 @c man end EXAMPLES
 
-@include syntax.texi
-@include eval.texi
-@include decoders.texi
-@include encoders.texi
-@include demuxers.texi
-@include muxers.texi
-@include indevs.texi
-@include outdevs.texi
-@include protocols.texi
-@include bitstream_filters.texi
-@include filters.texi
-@include metadata.texi
-
 @chapter See Also
 
 @ifhtml

doc/ffplay.texi

@@ -186,16 +186,6 @@ Seek to percentage in file corresponding to fraction of width.
 
 @c man end
 
-@include syntax.texi
-@include eval.texi
-@include decoders.texi
-@include demuxers.texi
-@include muxers.texi
-@include indevs.texi
-@include outdevs.texi
-@include protocols.texi
-@include filters.texi
-
 @chapter See Also
 
 @ifhtml

doc/ffprobe.texi

@@ -487,12 +487,6 @@ DV, GXF and AVI timecodes are available in format metadata
 @end itemize
 @c man end TIMECODE
 
-@include syntax.texi
-@include decoders.texi
-@include demuxers.texi
-@include protocols.texi
-@include indevs.texi
-
 @chapter See Also
 
 @ifhtml