RFR: JDK-8266506: [aix] Treat mapping attempt too close to BRK as a mapping error [v2]

[Thomas Stuefe]

> On AIX, in os::attempt_reserve_memory_at(), if the user specified a wish address too close to the BRK segment, we silently ignore the wish address and just map anywhere.
> 
> This is not the right behavior since the normal behavior when failing to map to a wish address is to return NULL (see JDK-8266419). Therefore we should return NULL in these cases instead.
> 
> This is a day zero bug.

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/3859/files
  - new: https://git.openjdk.java.net/jdk/pull/3859/files/6e65b6b5..a5297796

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3859&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3859&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3859.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3859/head:pull/3859

PR: https://git.openjdk.java.net/jdk/pull/3859