Reland "Check for semaphore alignment on posix platforms. (patchset #1 id:1 of https://codereview.chromium.org/1912923003/ )"

This patch also fixed three misaligned semaphores.

This reverts commit 80c73e2c.

BUG=chromium:605349
LOG=NO

Review URL: https://codereview.chromium.org/1917923002

Cr-Commit-Position: refs/heads/master@{#35773}