Review Request JDK-8188052: JNI_FindClass needs to specify the class loading context used for library lifecycle hooks

[mandy chung]

This patch separates the JNI `FindClass` issue from the review thread 
for JDK-8188052 [1] into a different issue.

webrev: 
http://cr.openjdk.java.net/~mchung/jdk10/webrevs/8188052/webrev.00/index.html

This patch changes `FindClass` to specify the class loading context used 
for the load and unload hook. `FindClass` when called from JNI_OnUnload 
is changed to use the system class loader as the context. This is an 
incompatible behavioral change and this bumps the version so that a 
native library can determine the new behavior if desire.  This change 
proposes to defines JNI_VERSION_10 and I expect this name will be 
revisited along with the version string for the proposed new release 
cadence [2].

CSR:  https://bugs.openjdk.java.net/browse/JDK-8188069

Thanks David for the suggested spec wordings.

thanks
Mandy
[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-September/049292.html
[2] 
http://mail.openjdk.java.net/pipermail/discuss/2017-September/004281.html