RFR: JDK-8291558: unify print_jni_name_prefix_on and print_jni_name_suffix_on on posix platforms

[Matthias Baesken]

print_jni_name_prefix_on and print_jni_name_suffix_on can be unified on the OpenJDK posix platforms.

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Commit messages:
 - JDK-8291558

Changes: https://git.openjdk.org/jdk/pull/9686/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9686&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291558
  Stats: 32 lines in 4 files changed: 8 ins; 24 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9686.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9686/head:pull/9686

PR: https://git.openjdk.org/jdk/pull/9686