RFR: 8286092: Remove dead windows stack code

[Coleen Phillimore]

In reviewing JDK-[8285832](https://bugs.openjdk.java.net/browse/JDK-8285832) @iklam noticed the code following the minimum stack size calculation is dead.  This change removes the dead code, plus an unused os_thread_counter nearby.
This code predates mercurial.
Tested with tier1 on windows-x64 and windows-x64-debug.

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Commit messages:
 - 8286092: Remove dead windows stack code

Changes: https://git.openjdk.java.net/jdk/pull/8524/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8524&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286092
  Stats: 37 lines in 2 files changed: 0 ins; 37 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8524.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8524/head:pull/8524

PR: https://git.openjdk.java.net/jdk/pull/8524