RFR 8168410: Multiple JCK tests are failing due to SecurityException is not thrown.

[Weijun Wang]

Please take a review at

     cr.openjdk.java.net/~weijun/8168410/webrev.00

JDK-8164705 introduced a compatibility layer to make sure that when 
FilePermission on "/pwd/x" is granted you can still read "x". The 
compatibility layer has 2 parts:

1. Inside our own default policy provider.

2. Inside ProtectionDomain.

Multiple JCK tests fail because of #2. After some discussion, we decide 
to only enable #2 when a new system property jdk.security.filePermCompat 
is set.

This means if user is using a customized policy implementation, the 
compatibility layer will not work, and granting a FilePermission on "x" 
will not allow the code reading "/pwd/x" when a security manager is on.

Hopefully this is acceptable because:

1. A customized policy implementation is seldom used.

2. After JDK-8164705, we advise users to update their policy file so 
that the FilePermission path matches how a file is actually accessed. So 
if an application is reading "/pwd/x", the permission on "/pwd/x" 
(instead if "x") should be granted.

Thanks
Max