Split the "Introduction" chapter in two chapters as suggested by

Diego.


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@20297 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

doc/vfilters.texi

@@ -28,6 +28,8 @@ integrate it into ffmpeg and ffplay.
 But note that there may still be serious bugs in the code and its API
 and ABI should not be considered stable yet!
 
+@chapter Tutorial
+
 In libavfilter, it is possible for filters to have multiple inputs and
 multiple outputs.
 To illustrate the sorts of things that are possible, we can