RFR: 8279936: Change shared code to use os:: system API's

[Harold Seigel]

Please review this small change to call os:: API's.  the changes were tested with Mach5 tiers 1-2 on Linux, Mac OS, and Windows, and Mach5 tiers 3-5 on Linux x64.  Most of these changes were for I/O related calls.  Changes to memory allocation calls such as malloc and free will be handled in a future change.

Thanks, Harold

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Commit messages:
 - 8279936: Change shared code to use os:: system API's

Changes: https://git.openjdk.java.net/jdk/pull/7055/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7055&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279936
  Stats: 25 lines in 9 files changed: 1 ins; 0 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7055.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7055/head:pull/7055

PR: https://git.openjdk.java.net/jdk/pull/7055