Small Patch for "ffplay -" instead of "ffplay pipe:" by (Bill Eldridge <bill at rfa dot org>)

Originally committed as revision 2181 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffplay.c

@@ -1660,6 +1660,8 @@ void show_help(void)
 
 void parse_arg_file(const char *filename)
 {
+    if (!strcmp(filename, "-"))
+                    filename = "pipe:";
     input_filename = filename;
 }