Suppress the now most common warning in the Windows JavaHL build.

* subversion/bindings/javahl/native/JNIUtil.h
  (isJavaExceptionThrown): Suppress warning on casting jboolean to bool.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1544260 13f79535-47bb-0310-9956-ffa450edef68