Add preliminary output/encoder interface

- First, I redid the output interface for libobs.  I feel like it's
  going in a pretty good direction in terms of design.

  Right now, the design is so that outputs and encoders are separate.
  One or more outputs can connect to a specific encoder to receive its
  data, or the output can connect directly to raw data from libobs
  output itself, if the output doesn't want to use a designated encoder.
  Data is received via callbacks set when you connect to the encoder or
  raw output.  Multiple outputs can receive the data from a single
  encoder context if need be (such as for streaming to multiple channels
  at once, and/or recording with the same data).

  When an encoder is first connected to, it will connect to raw output,
  and start encoding.  Additional connections will receive that same
  data being encoded as well after that.  When the last encoder has
  disconnected, it will stop encoding.  If for some reason the encoder
  needs to stop, it will use the callback with NULL to signal that
  encoding has stopped.  Some of these things may be subject to change
  in the future, though it feels pretty good with this design so far.
  Will have to see how well it works out in practice versus theory.

- Second, Started adding preliminary RTMP/x264 output plugin code.

  To speed things up, I might just make a direct raw->FFmpeg output to
  create a quick output plugin that we can start using for testing all
  the subsystems.

libobs/obs-encoder.h

@@ -0,0 +1,147 @@
+/******************************************************************************
+    Copyright (C) 2013 by Hugh Bailey <obs.jim@gmail.com>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+******************************************************************************/
+
+#pragma once
+
+#include "util/c99defs.h"
+#include "util/dstr.h"
+
+/*
+ * ===========================================
+ *  Outputs 
+ * ===========================================
+ *
+ *   An output takes raw audio and/or video and processes and/or outputs it
+ * to a destination, whether that destination be a file, network, or other.
+ *
+ *   A module with outputs needs to export these functions:
+ *       + enum_outputs
+ *
+ *   Each individual output is then exported by it's name.  For example, an
+ * output named "myoutput" would have the following exports:
+ *       + myoutput_getname
+ *       + myoutput_create
+ *       + myoutput_destroy
+ *       + myoutput_start
+ *       + myoutput_stop
+ *       + myoutput_encoders
+ *
+ *       [and optionally]
+ *       + myoutput_setencoder
+ *       + myoutput_getencoder
+ *       + myoutput_config
+ *       + myoutput_pause
+ *
+ * ===========================================
+ *   Primary Exports
+ * ===========================================
+ *   const char *enum_outputs(size_t idx);
+ *       idx: index of the output.
+ *       Return value: Output identifier name.  NULL when no more available.
+ *
+ * ===========================================
+ *   Output Exports
+ * ===========================================
+ *   const char *[name]_getname(const char *locale);
+ *       Returns the full translated name of the output type (seen by the user).
+ *
+ * ---------------------------------------------------------
+ *   void *[name]_create(const char *settings, obs_output_t output);
+ *       Creates an output.
+ *
+ *       settings: Settings of the output.
+ *       output: pointer to main output
+ *       Return value: Internal output pointer, or NULL if failed.
+ *
+ * ---------------------------------------------------------
+ *   void [name]_destroy(void *data);
+ *       Destroys the output.
+ *
+ * ---------------------------------------------------------
+ *   void [name]_update(void *data, const char *settings)
+ *       Updates the output's settings
+ *
+ *       settings: New settings of the output
+ *
+ * ---------------------------------------------------------
+ *   bool [name]_reset(void *data)
+ *       Starts output
+ *
+ *       Return value: true if successful
+ *
+ * ---------------------------------------------------------
+ *   int [name]_encode(void *data, void *frames, size_t size,
+ *                      struct encoder_packet **packets)
+ *
+ *       frames: frame data
+ *       size: size of data pointed to by the frame parameter
+ *       packets: returned packets, or NULL if none
+ *       Return value: number of output frames
+ *
+ * ---------------------------------------------------------
+ *   bool [name]_reset(void *data)
+ *       Resets encoder data
+ *
+ *       Return value: true if successful
+ *
+ * ===========================================
+ *   Optional Output Exports
+ * ===========================================
+ *   void [name]_setbitrate(void *data, uint32_t bitrate, uint32_t buffersize);
+ *       Sets the bitrate of the encoder
+ */
+
+struct obs_encoder;
+
+struct encoder_info {
+	const char *id;
+
+	const char *(*getname)(const char *locale);
+
+	void *(*create)(const char *settings, struct obs_encoder *encoder);
+	void (*destroy)(void *data);
+
+	void (*update)(void *data, const char *settings);
+
+	bool (*reset)(void *data);
+
+	int (*encode)(void *data, void *frames, size_t size,
+			struct encoder_packet **packets);
+	int (*getheader)(void *data, struct encoder_packet **packets);
+
+	/* optional */
+	void (*setbitrate)(void *data, uint32_t bitrate, uint32_t buffersize);
+	void (*request_keyframe)(void *data);
+};
+
+struct obs_encoder_callback {
+	void (*new_packet)(void *param, struct encoder_packet *packet);
+	void *param;
+};
+
+struct obs_encoder {
+	char                                *name;
+	void                                *data;
+	struct encoder_info                 callbacks;
+	struct dstr                         settings;
+
+	pthread_mutex_t                     data_callbacks_mutex;
+	DARRAY(struct obs_encoder_callback) data_callbacks;
+};
+
+extern bool load_encoder_info(void *module, const char *module_name,
+		const char *encoder_name, struct encoder_info *info);