[8u] RFR(xs): 8068042: Check jdk/src/share/native/sun/misc/URLClassPath.c for JNI pending exception

[Calvin Cheung]

Please review this small fix for adding the check for JNI pending 
exception in URLClassPath.c.

This fix is only for jdk8u and isn't applicable to 9.

JBS: https://bugs.openjdk.java.net/browse/JDK-8068042
       (unfortunately it is a closed bug)

webrev: http://cr.openjdk.java.net/~ccheung/8068042_8u/webrev.00/

Tests:
     JPRT with -testset hotspot
     RBT hotspot/test/:hotspot_all,vm.regression.testlist, vm.quick

thanks,
Calvin