RFR: JDK-8035340 - (prefs) Check jdk/src/windows/native/java/util/WindowsPreference.c for JNI pending exceptions

[Mark Sheppard]

Hi
    Please oblige and review the following changes
http://cr.openjdk.java.net/~msheppar/8035340/webrev/

which address the issues raised in
https://bugs.openjdk.java.net/browse/JDK-8035340

This effort adds NULL checks and pending exception check after
JNI calls and adds NULL check to malloc calls in WindowsPreferences.c
This is a Windows change set.

regards
Mark