Fix grammar for avfilter_graph_parse() doxy.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@18900 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavfilter/graphparser.h

@@ -37,7 +37,7 @@ typedef struct AVFilterInOut {
 } AVFilterInOut;
 
 /**
- * Add to a graph a graph described by a string.
+ * Adds a graph described by a string to a graph.
  *
  * @param graph   the filter graph where to link the parsed graph context
  * @param filters string to be parsed