RFR: JDK-8289143: JDK-6980847 broke 32-bit builds

[Thomas Stuefe]

Trivial fix to get 32-bit to build again.

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

Commit messages:
 - use jlong_to_ptr

Changes: https://git.openjdk.org/jdk/pull/9275/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9275&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289143
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9275.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9275/head:pull/9275

PR: https://git.openjdk.org/jdk/pull/9275