stream: doc: stream_extractor_AttachParsed fixes

- Rename the source argument to stream, which is the actual name of
  the argument.
- Add documentation for the data argument
- Add missing group, without this doxygen would list it twice in
  places like search, leading to some confusion.

src/input/stream.h

@@ -91,6 +91,11 @@ stream_t *stream_FilterAutoNew( stream_t *source ) VLC_USED;
  */
 stream_t *stream_FilterChainNew( stream_t *source, const char *list ) VLC_USED;
 
+/**
+ * \addtogroup stream_extractor_Internals
+ * @{
+ */
+
 /**
  * Attach \ref stream_extractor%s according to specified data
  *
@@ -110,9 +115,10 @@ stream_t *stream_FilterChainNew( stream_t *source, const char *list ) VLC_USED;
  *          stream-extractors referred to by `psz_data`, something which is not
  *          guaranteed.
  *
- * \param[out] source a pointer-to-pointer to stream where the attached
+ * \param[out] stream a pointer-to-pointer to stream where the attached
  *             stream-extractor will be applied. `*stream` will refer
  *             to the last successful attachment.
+ * \param      data the fragment data string to parse.
  * \param[out] out_extra `*out_extra` will point to any additional data
  *             in `psz_data` that does not specify an entity (if any).
  * \return VLC_SUCCESS on success, an error-code on failure
@@ -120,4 +126,8 @@ stream_t *stream_FilterChainNew( stream_t *source, const char *list ) VLC_USED;
 int stream_extractor_AttachParsed( stream_t** stream, const char* data,
                                    char const** out_extra );
 
+/**
+ * @}
+ */
+
 #endif