RFR: JDK-8035571 - Check jdk/src/windows/native/java/net/TwoStacksPlain* for JNI pending exceptions

[Mark Sheppard]

Hi
    Please oblige and review the following changes
http://cr.openjdk.java.net/~msheppar/8035571/webrev/

which address the issue raised in
https://bugs.openjdk.java.net/browse/JDK-8035571

summary:
JNI return value and pending exception checks added