spelling/grammar fixes for a Doxygen comment

Originally committed as revision 8136 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/Makefile

@@ -24,9 +24,7 @@ HEADERS = avutil.h common.h mathematics.h integer.h rational.h \
           random.h
 
 NAME=avutil
-ifeq ($(BUILD_SHARED),yes)
 LIBVERSION=$(LAVUVERSION)
 LIBMAJOR=$(LAVUMAJOR)
-endif
 
 include ../common.mak

libavutil/tree.h

@@ -41,10 +41,10 @@ void *av_tree_find(const struct AVTreeNode *root, void *key, int (*cmp)(void *ke
  *              root node can change during insertions, this is required to
  *              keep the tree balanced
  *
- * @return if no insertion happened, the found element
- *         if a insertion happened, then either key or NULL is returned (which it is
- *         depends on the tree state and the implemenattion, you should make no
- *         asumtations that its one or the other in code)
+ * @return If no insertion happened, the found element.
+ *         If an insertion happened, then either key or NULL is returned (which one
+ *         it is depends on the tree state and the implementation, you should make
+ *         no assumptions that it's one or the other in the code).
  */
 void *av_tree_insert(struct AVTreeNode **rootp, void *key, int (*cmp)(void *key, const void *b));
 void av_tree_destroy(struct AVTreeNode *t);