RFR: 8258837: Remove JVM option DisableStartThread

[Harold Seigel]

Please review this small change to remove option DisableStartThread.  The change was tested with Mach5 tiers 1 and 2 on Linux, Mac OS, and Windows and tiers 3-5 on Linux x64.

Thanks, Harold

-------------

Commit messages:
 - 8258837: Remove JVM option DisableStartThread

Changes: https://git.openjdk.java.net/jdk/pull/1879/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1879&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258837
  Stats: 19 lines in 2 files changed: 1 ins; 9 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1879.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1879/head:pull/1879

PR: https://git.openjdk.java.net/jdk/pull/1879