RFR[S] 8191927 Enable AppCDS for custom loaders on all 64-bit Linux and AIX

[Ioi Lam]

Hi,

Please review this change to support AppCDS on all 64-bit Linux 
platforms as well as AIX.

     https://bugs.openjdk.java.net/browse/JDK-8191927
http://cr.openjdk.java.net/~iklam/jdk10/8191927-appcds-custom-loader-for-more-platforms.v01/

The patch must be applied on top of the AppCDS patch:

http://cr.openjdk.java.net/~iklam/jdk10/8188791-open-appcds.v03/

The patch was initially contributed by Volker Simonis. I modified it a 
little to avoid repeating the platform enumerations in all the test 
cases. Instead, I added a new test property, so the tests that require 
AppCDS support for custom loaders can be written as:

     * @requires vm.cds.custom.loaders

I've tested on Linux manually, and I am now running on all of the 
Oracle-supported platforms using our internal test harness.

Thanks
- Ioi