RFR: JDK-8295889: NMT preinit code does not handle allocation errors

[Thomas Stuefe]

The NMT preinit allocator (used for os::malloc and friends before the VM is initialized) does not handle malloc errors, nor does it handle overflows due to large sizes (it uses malloc headers too). Both cases need to be handled.

However, we can keep matters very simple. No need to propagate errors up to the caller; we can just fatal out on errors here since, in this phase, there is no alternative for failed allocations.

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Commit messages:
 - JDK-8295889-NMT-preinit-should-handle-allocation-errors

Changes: https://git.openjdk.org/jdk/pull/10855/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10855&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295889
  Stats: 38 lines in 2 files changed: 38 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10855.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10855/head:pull/10855

PR: https://git.openjdk.org/jdk/pull/10855