Currency.isPastCutoverDate should be made more robust

The changes for 7180362 are here:

http://hg.openjdk.java.net/jdk8/tl/jdk/rev/fffbb33df102

One oddity with this code is that isPastCutoverDate is declared to throw NullPointerExcepiton and IndexOutOfBoundsException but they are runtime exceptions. Furthermore the caller (replaceCurrencyData) is catching and ignoring these exceptions which is very odd and potentially could hide other bugs that cause NullPointerExcepiton to be thrown.

This bug is submitted as a reminder that this code should re-examined and cleaned up. This should be done before the changes are back-ported to jdk7u.