RFR: 8256306: ObjectMonitor::_contentions field should not be 'jint'

[Coleen Phillimore]

I changed the _contentions and _waiters fields from jint to int and ran tests tier1-3.  Tested tier1 with linux, mac, windows platforms. Also changed the _previous_owner_tid to unintptr_t from jlong, since that's what the cast did.

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Commit messages:
 - 8256306: ObjectMonitor::_contentions field should not be 'jint'

Changes: https://git.openjdk.java.net/jdk/pull/3980/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3980&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256306
  Stats: 27 lines in 5 files changed: 1 ins; 0 del; 26 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3980.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3980/head:pull/3980

PR: https://git.openjdk.java.net/jdk/pull/3980