Clarify public domain statement similar to qt-faststart.c.

Originally committed as revision 9574 to svn://svn.ffmpeg.org/ffmpeg/trunk

cws2fws.c

 /*
  * cws2fws by Alex Beregszaszi
- * Public domain.
+ * This file is placed in the public domain.
+ * Use the program however you see fit.
  *
  * This utility converts compressed Macromedia Flash files to uncompressed ones.
  */