RFR: 8025734: Use literal IP address where possible in SocketPermission generated by HttpURLPermission

[Michael McMahon]

Hi,

This change updates HttpURLPermission to grant a SocketPermission with a 
literal IP address
rather than the String hostname when the IP address is available (this 
gets looked up anyway.
So, we're not adding any additional name service lookups). By granting a 
permission with
a literal IP address it avoids the complicated isUntrusted() logic in 
SocketPermission
where possible. The change also enables the use of the limited 
doPrivileged logic.
I thought it would be better to enable this in a smaller change than the 
bigger API change
coming later.

This change includes a test of HttpURLPermission using a dummy 
nameservice. It is
a basic smoke test that checks SecurityException is being thrown (or 
not) when expected
as opposed to an IOException for unknown hostnames.

http://cr.openjdk.java.net/~michaelm/8025734/webrev.1/

Thanks
Michael.