RFR: JDK-8266419: [aix] in mmap mode, os::attempt_reserve_memory_at() fails to handle wrong mapping address [v2]

[Thomas Stuefe]

> On AIX, in mmap() mode, if the mmap call succeeds but not at the requested address, the mapping should be unmapped and the operation should count as error - like it is done on all other platforms.
> 
> (AFAICS this is a day zero bug in our port - mmap mode is seldomly used).
> 
> Tested: Nightlies at SAP with and without 4K pages.

Thomas Stuefe has updated the pull request incrementally with one additional commit since the last revision:

  Modify log message

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3834/files
  - new: https://git.openjdk.java.net/jdk/pull/3834/files/138fae89..074e73d7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3834&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3834&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3834.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3834/head:pull/3834

PR: https://git.openjdk.java.net/jdk/pull/3834