lavu: bump minor and add APIchanges entry for AV_PICTURE_TYPE_NONE

The symbols was added in the git commit
512933671409f9f88cc9fdfc8f29525d32240bab.

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2011-06-28 - 5129336 - lavu 51.11.0 - avutil.h
+  Define the AV_PICTURE_TYPE_NONE value in AVPictureType enum.
+
 2011-06-19 - xxxxxxx - lavfi 2.23.0 - avfilter.h
   Add layout negotiation fields and helper functions.
 

libavutil/avutil.h

@@ -40,7 +40,7 @@
 #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
 
 #define LIBAVUTIL_VERSION_MAJOR 51
-#define LIBAVUTIL_VERSION_MINOR 10
+#define LIBAVUTIL_VERSION_MINOR 11
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \