Drop @ documentation references from functions and external types

`@` references are used to reference function parameters, struct members
or enum variants _within_ the current type/function.  It cannot and
should not be used to reference to types outside that.

Since C has no notion of member functions it makes little sense to
prefix these with `@`; most of the documentation here was referencing
functions on _different_ types anyway.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1090>

gst-libs/gst/audio/gstaudiobasesink.h

@@ -110,7 +110,7 @@ typedef struct _GstAudioBaseSinkPrivate GstAudioBaseSinkPrivate;
  * @GST_AUDIO_BASE_SINK_DISCONT_REASON_FLUSH: Samples have been flushed
  * @GST_AUDIO_BASE_SINK_DISCONT_REASON_SYNC_LATENCY: Sink was synchronized to the estimated latency (occurs during initialization)
  * @GST_AUDIO_BASE_SINK_DISCONT_REASON_ALIGNMENT: Aligning buffers failed because the timestamps are too discontinuous
- * @GST_AUDIO_BASE_SINK_DISCONT_REASON_DEVICE_FAILURE: Audio output device experienced and recovered from an error but introduced latency in the process (see also @gst_audio_base_sink_report_device_failure())
+ * @GST_AUDIO_BASE_SINK_DISCONT_REASON_DEVICE_FAILURE: Audio output device experienced and recovered from an error but introduced latency in the process (see also gst_audio_base_sink_report_device_failure())
  *
  * Different possible reasons for discontinuities. This enum is useful for the custom
  * slave method.

gst-libs/gst/video/gstvideoutils.h

@@ -55,8 +55,8 @@ typedef struct _GstVideoCodecFrame GstVideoCodecFrame;
  * respective @set_format vmethods.
  *
  * Decoders and encoders can set the downstream state, by using the
- * @gst_video_decoder_set_output_state() or
+ * gst_video_decoder_set_output_state() or
- * @gst_video_encoder_set_output_state() methods.
+ * gst_video_encoder_set_output_state() methods.
  */
 struct _GstVideoCodecState
 {
@@ -223,8 +223,8 @@ typedef enum
  *           be kept.
  * @output_buffer: the output #GstBuffer. Implementations should set this either
  *           directly, or by using the
- *           @gst_video_decoder_allocate_output_frame() or
+ *           gst_video_decoder_allocate_output_frame() or
- *           @gst_video_decoder_allocate_output_buffer() methods. The buffer is
+ *           gst_video_decoder_allocate_output_buffer() methods. The buffer is
  *           owned by the frame and references to the frame instead of the
  *           buffer should be kept.
  * @deadline: Running time when the frame will be used.

gst-libs/gst/video/video-color.c

@@ -547,7 +547,7 @@ gst_video_color_transfer_decode (GstVideoTransferFunction func, gdouble val)
  * @val: a value
  *
  * Convert @val to its gamma decoded value. This is the inverse operation of
- * @gst_video_color_transfer_encode().
+ * gst_video_color_transfer_encode().
  *
  * For a non-linear value L' in the range [0..1], conversion to the linear
  * L is in general performed with a power function like:

gst/rawparse/gstrawbaseparse.c

@@ -91,8 +91,8 @@
  *   which contains caps from the updated configuration.
  *
  * * In case there are bytes in each frame that aren't part of the actual
- *   payload, the get_overhead_size() vfunc must be defined, and the
+ *   payload, the `get_overhead_size()` vfunc must be defined, and the
- *   @get_config_frame_size() vfunc must return a frame size that includes
+ *   `get_config_frame_size()` vfunc must return a frame size that includes
  *   the number of non-payload bytes (= the overhead). Otherwise, the
  *   timestamps will incorrectly include the overhead bytes.
  */