Implement RTMP module (still needs drop code)

- Implement the RTMP output module.  This time around, we just use a
   simple FLV muxer, then just write to the stream with RTMP_Write.
   Easy and effective.

 - Fix the FLV muxer, the muxer now outputs proper FLV packets.

 - Output API:
   * When using encoders, automatically interleave encoded packets
     before sending it to the output.

   * Pair encoders and have them automatically wait for the other to
     start to ensure sync.

   * Change 'obs_output_signal_start_fail' to 'obs_output_signal_stop'
     because it was a bit confusing, and doing this makes a lot more
     sense for outputs that need to stop suddenly (disconnections/etc).

 - Encoder API:
   * Remove some unnecessary encoder functions from the actual API and
     make them internal.  Most of the encoder functions are handled
     automatically by outputs anyway, so there's no real need to expose
     them and end up inadvertently confusing plugin writers.

   * Have audio encoders wait for the video encoder to get a frame, then
     start at the exact data point that the first video frame starts to
     ensure the most accrate sync of video/audio possible.

   * Add a required 'frame_size' callback for audio encoders that
     returns the expected number of frames desired to encode with.  This
     way, the libobs encoder API can handle the circular buffering
     internally automatically for the encoder modules, so encoder
     writers don't have to do it themselves.

 - Fix a few bugs in the serializer interface.  It was passing the wrong
   variable for the data in a few cases.

 - If a source has video, make obs_source_update defer the actual update
   callback until the tick function is called to prevent threading
   issues.

libobs/obs.h

@@ -751,6 +751,9 @@ EXPORT void obs_output_set_audio_conversion(obs_output_t output,
 EXPORT bool obs_output_can_begin_data_capture(obs_output_t output,
 		uint32_t flags);
 
+/** Initializes encoders (if any) */
+EXPORT bool obs_output_initialize_encoders(obs_output_t output, uint32_t flags);
+
 /**
  * Begins data capture from media/encoders.
  *
@@ -768,8 +771,13 @@ EXPORT bool obs_output_begin_data_capture(obs_output_t output, uint32_t flags);
 /** Ends data capture from media/encoders */
 EXPORT void obs_output_end_data_capture(obs_output_t output);
 
-/** Signals that start failed */
-EXPORT void obs_output_signal_start_fail(obs_output_t output, int code);
+/**
+ * Signals that the output has stopped itself.
+ *
+ * @param  output  Output context
+ * @param  code    Error code (or OBS_OUTPUT_SUCCESS if not an error)
+ */
+EXPORT void obs_output_signal_stop(obs_output_t output, int code);
 
 
 /* ------------------------------------------------------------------------- */
@@ -787,7 +795,7 @@ EXPORT const char *obs_encoder_getdisplayname(const char *id,
  * @param  video     Video output context to encode data from
  * @return           The video encoder context, or NULL if failed or not found.
  */
-EXPORT obs_encoder_t obs_encoder_create_video(const char *id, const char *name,
+EXPORT obs_encoder_t obs_video_encoder_create(const char *id, const char *name,
 		obs_data_t settings, video_t video);
 
 /**
@@ -799,39 +807,12 @@ EXPORT obs_encoder_t obs_encoder_create_video(const char *id, const char *name,
  * @param  audio     Audio output context to encode data from
  * @return           The video encoder context, or NULL if failed or not found.
  */
-EXPORT obs_encoder_t obs_encoder_create_audio(const char *id, const char *name,
+EXPORT obs_encoder_t obs_audio_encoder_create(const char *id, const char *name,
 		obs_data_t settings, audio_t audio);
 
 /** Destroys an encoder context */
 EXPORT void obs_encoder_destroy(obs_encoder_t encoder);
 
-/**
- * Initializes the encoder and returns whether settings are valid.
- * Must be called before obs_encoder_start
- */
-EXPORT bool obs_encoder_initialize(obs_encoder_t encoder);
-
-/**
- * Starts encoding.  This function can be called more than once, and each
- * callback will receive the same encoder data.
- *
- * @param  encoder     Encoder context
- * @param  new_packet  Callback that receives encoded packets
- * @param  param       Callback parameter
- */
-EXPORT void obs_encoder_start(obs_encoder_t encoder,
-		void (*new_packet)(void *param, struct encoder_packet *packet),
-		void *param);
-
-/**
- * Stops encoding.  You must use the same callback/parameter combination that
- * was used for obs_encoder_start.  Only when the last callback has been
- * removed will all encoding stop.
- */
-EXPORT void obs_encoder_stop(obs_encoder_t encoder,
-		void (*new_packet)(void *param, struct encoder_packet *packet),
-		void *param);
-
 /** Returns the codec of the encoder */
 EXPORT const char *obs_encoder_get_codec(obs_encoder_t encoder);