RFR: JDK-8027698: Platform specific jars are not being signed by the sign-jars target

[Erik Joelsson]

Please review this simple fix, adding sunmscapi.jar and ucrypto.jar to 
the list of jars to be signed by the sign-jars target. Since these jars 
are platform dependent, they aren't always present.

Bug: https://bugs.openjdk.java.net/browse/JDK-8027698
Webrev: http://cr.openjdk.java.net/~erikj/8027698/webrev.jdk.01/
/Erik