hg: jdk/sandbox: 8191053: Provide a mechanism to make system's security manager immutable

[chris.hegarty at oracle.com]

Changeset: ec4f2762b234
Author:    mullan
Date:      2018-10-10 16:25 -0400
URL:       http://hg.openjdk.java.net/jdk/sandbox/rev/ec4f2762b234

8191053: Provide a mechanism to make system's security manager immutable
Summary: Make System.setSecurityManager optional to support and add new disallow and allow options to the java.security.manager system property
Reviewed-by: alanb, mchung, rriggs, smarks

! src/java.base/share/classes/java/lang/SecurityManager.java
! src/java.base/share/classes/java/lang/System.java
+ test/jdk/java/lang/System/AllowSecurityManager.java