Updated copyright notices to remove LIBGCJ_LICENSE references

[Mark Wielaard]

Hi,

The following files were merged from libgcj but still refered to the
LIBGCJ_LICENSE file. I have updated the copyright notice on these files
so they are the same as the other Classpath copyright notices.

    * java/io/DataInputStream.java: update copyright notice
    * java/io/PrintWriter.java: idem
    * java/io/Reader.java: idem
    * java/io/StreamTokenizer.java: idem
    * java/io/StringReader.java: idem
    * java/lang/reflect/ReflectPermission.java: idem

Cheers,

Mark