Fix problem latest compatibility problem. [1769]

Prior to this commit, McV’s override of IdvPersistenceManager appeared
to want to “use” the older version of IOUtil’s “writeTo” method (the
one that returned an integer):

IOUtil.writeTo(Ljava/io/InputStream;Ljava/io/OutputStream;)I

All of the applicable “writeTo” methods in IOUtil have been changed to
return longs, so it is not clear to me where the reference to the old
definition is coming from (running “ant clean” does nothing).
Regardless, changing the method call in IdvPersistenceManager to
reference exactly the method that we want called seems to work:

IOUtil.writeTo(IOUtil.getInputStream(file, getClass()), zos, null, 0L);