8197531: Miscellaneous changes imported from jsr166 CVS 2018-04

Reviewed-by: martin, psandoz

src/java.base/share/classes/java/util/concurrent/CompletableFuture.java

@@ -2883,7 +2883,7 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
             STACK = l.findVarHandle(CompletableFuture.class, "stack", Completion.class);
             NEXT = l.findVarHandle(Completion.class, "next", Completion.class);
         } catch (ReflectiveOperationException e) {
-            throw new Error(e);
+            throw new ExceptionInInitializerError(e);
         }
 
         // Reduce the risk of rare disastrous classloading in first call to