obs-ffmpeg: Separate logging code

Cleans up obs-ffmpeg.c and separates all the logging code to a different
file, which can be enabled with ENABLE_FFMPEG_LOGGING.

plugins/obs-ffmpeg/obs-ffmpeg-config.h.in

@@ -0,0 +1,17 @@
+#ifndef ON
+#define ON 1
+#endif
+
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+#ifndef OFF
+#define OFF 0
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+#define ENABLE_FFMPEG_LOGGING @ENABLE_FFMPEG_LOGGING@