RFR: 6782021: add support for localmachine keystores on windows

[Mat Carter]

On Windows you can now access the local machine keystores using the strings "Windows-MY-LOCALMACHINE" and "Windows-ROOT-LOCALMACHINE"; note the application requires admin privileges.

"Windows-MY" and "Windows-ROOT" remain unchanged, however given these original keystore strings mapped to the current user, I added  "Windows-MY-CURRENTUSER" and "Windows-ROOT-CURRENTUSER" so that a developer can explicitly specify the current user location.  These two new strings simply map to the original two strings, i.e. no duplication of code paths etc

No new tests added, keystore functionality and API remains unchanged, the local machine keystore types would require the tests to run in admin mode

Tested on windows, passes tier1 and tier2 tests

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Commit messages:
 - 6782021: add support for localmachine keystores on windows

Changes: https://git.openjdk.java.net/jdk/pull/8210/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8210&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-6782021
  Stats: 79 lines in 4 files changed: 66 ins; 0 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8210.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8210/head:pull/8210

PR: https://git.openjdk.java.net/jdk/pull/8210