dict: fix various typos

libavutil/dict.h

@@ -21,11 +21,10 @@
  * @file Public dictionary API.
  * @deprecated
  *  AVDictionary is provided for compatibility with libav. It is both in
- *  implementation as well as API inefficient. It doesnt scale and is
- *  be extreemly slow with large dictionaries.
- *  It is recommanded that new code uses our tree container from tree.c/h
- *  where applicable.
- *  Which uses AVL trees to achive O(log n) performance
+ *  implementation as well as API inefficient. It does not scale and is
+ *  extremely slow with large dictionaries.
+ *  It is recommended that new code uses our tree container from tree.c/h
+ *  where applicable, which uses AVL trees to achive O(log n) performance.
  */
 
 #ifndef AVUTIL_DICT_H