Remove explicit filename from Doxygen @file commands.

Passing an explicit filename to this command is only necessary if the
documentation in the @file block refers to a file different from the
one the block resides in.

Originally committed as revision 22921 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/api-example.c

@@ -19,7 +19,7 @@
  */
 
 /**
- * @file libavcodec/apiexample.c
+ * @file
  * avcodec API use example.
  *
  * Note that this library only handles codecs (mpeg, mpeg4, etc...),