MIPS: Fix unaligned memory access.

MIPS: Fix unaligned memory access.

On MIPS32 we can't read a 8 bytes long data from a not 8 bytes aligned memory address.

BUG=
TEST=mjsunit/debug-backtrace

Committed: https://crrev.com/0acc511e62fbd717e335c700012de47827fe0630
Cr-Commit-Position: refs/heads/master@{#29100}

[balazs.kilvady, 2015-06-17 16:07:12]

balazs.kilvady@imgtec.com changed reviewers:
+ akos.palfi@imgtec.com, bmeurer@chromium.org, danno@chromium.org,
dusan.milosavljevic@imgtec.com, jarin@chromium.org, jkummerow@chromium.org,
paul.lind@imgtec.com

[balazs.kilvady, 2015-06-17 16:10:46]

This does need a v8-team review. PTAL if alignment fix is acceptable in v8 this
way or please let us know if there is any better approach.

[paul.l..., 2015-06-17 16:14:17]

lgtm

[Benedikt Meurer, 2015-06-18 06:14:16]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-06-18 06:14:17]

lgtm

[commit-bot: I haz the power, 2015-06-18 06:14:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1193433002/20001

[commit-bot: I haz the power, 2015-06-18 07:01:29]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-18 07:01:49]

Patchset 2 (id:??) landed as
https://crrev.com/0acc511e62fbd717e335c700012de47827fe0630
Cr-Commit-Position: refs/heads/master@{#29100}