This reverts commit 32f30f63.

Reason for revert: broken Fuchsia build, https://logs.chromium.org/v/?s=chromium%2Fbb%2Fclient.v8%2FV8_Fuchsia%2F460%2F%2B%2Frecipes%2Fsteps%2Fcompile%2F0%2Fstdout

Original change's description:
> [platform] check return values from memory operations
> 
> This change adds DCHECKs for calls such as mprotect, as well as marking some of
> the memory allocation and deallocation routines as V8_MUST_USE_RESULT. This
> additional checking gives us more useful information for failure in the presence
> of, for example, address space exhaustion.
> 
> Bug: 
> Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
> Change-Id: I5bc76c1da6160262d3d556fea49d284ddd4e02c5
> Reviewed-on: https://chromium-review.googlesource.com/721267
> Commit-Queue: Eric Holk <eholk@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49164}

TBR=hpayer@chromium.org,mlippautz@google.com,eholk@chromium.org

Change-Id: Ie4b57b45c801dcce7884645f50ff74f833de6dc4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/756137Reviewed-by: Eric Holk <eholk@chromium.org>
Commit-Queue: Eric Holk <eholk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49165}