RFR: 8312180: (bf) MappedMemoryUtils passes incorrect arguments to msync (aix) [v3]

[Tyler Steele]

> This change is as an alternate solution to my original proposal for [JDK-8312180](https://bugs.openjdk.org/browse/JDK-8312180).
> 
> Suggested by @tstuefe.
> 
> This change matches the return value of Bits.pageSize with the system page size (which is not currently true on AIX).
> 
> These tests are upstream of my target test (TestByteBuffer) and results are encouraging. Tier1 testing ~in ongoing for this change~ passes with flying colours.

Tyler Steele has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Removes include unistd & replaces it with util/globalDefs.hpp
 - Replace os::vm_page_size call with sysconf(_SC_PAGESIZE) on AIX in javaClasses.cpp

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

Changes: https://git.openjdk.org/jdk/pull/14963/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14963&range=02
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14963.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14963/head:pull/14963

PR: https://git.openjdk.org/jdk/pull/14963