RFR: 8277531: Print actual default stacksize on Windows thread logging

[Takuya Kiriyama]

I modified to log actual stack size on Windows by using `os::win32::default_stack_size()`.
Could you please review this fix?

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Commit messages:
 - 8277531: Print actual default stacksize on Windows thread logging

Changes: https://git.openjdk.java.net/jdk/pull/6495/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6495&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277531
  Stats: 45 lines in 2 files changed: 44 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6495.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6495/head:pull/6495

PR: https://git.openjdk.java.net/jdk/pull/6495