doxygen: place empty line between brief description and detailed description

Without it, Doxygen cannot separate them into different sections.

libavcodec/8svx.c

@@ -23,6 +23,7 @@
  * @file
  * 8svx audio decoder
  * @author Jaikrishnan Menon
+ *
  * supports: fibonacci delta encoding
  *         : exponential encoding
  */

libavcodec/qdm2.c

@@ -26,6 +26,7 @@
  * @file
  * QDM2 decoder
  * @author Ewald Snel, Benjamin Larsson, Alex Beregszaszi, Roberto Togni
+ *
  * The decoder is not perfect yet, there are still some distortions
  * especially on files encoded with 16 or 8 subbands.
  */

libavcodec/rl2.c

@@ -23,6 +23,7 @@
  * RL2 Video Decoder
  * @file
  * @author Sascha Sommer (saschasommer@freenet.de)
+ *
  * For more information about the RL2 format, visit:
  *   http://wiki.multimedia.cx/index.php?title=RL2
  */

libavformat/iss.c

@@ -23,7 +23,8 @@
  * @file
  * Funcom ISS file demuxer
  * @author Jaikrishnan Menon
- * for more information on the .iss file format, visit:
+ *
+ * For more information on the .iss file format, visit:
  * http://wiki.multimedia.cx/index.php?title=FunCom_ISS
  */
 

libavformat/rl2.c

@@ -23,6 +23,7 @@
  * RL2 file demuxer
  * @file
  * @author Sascha Sommer (saschasommer@freenet.de)
+ *
  * For more information regarding the RL2 file format, visit:
  *   http://wiki.multimedia.cx/index.php?title=RL2
  *