MIPS64: Fix exception return from regexp CheckStackGuardState().

MIPS64: Fix exception return from regexp CheckStackGuardState().

Lack of sign extension on simulator builds gives bad value for
RETRY and EXCEPTION codes.

TEST=mjsunit/regexp-stack-overflow, regress-crbug-467047
BUG=v8:3992
LOG=n

Committed: https://crrev.com/5b760434814ade98f84aef8dd54e8c888f12de15
Cr-Commit-Position: refs/heads/master@{#27553}

[paul.l..., 2015-03-28 19:05:54]

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

[paul.l..., 2015-03-28 19:05:54]

PTAL, also see the discussion v8:3992.

[dusmil.imgtec, 2015-03-30 13:09:15]

LGTM, Exactly as I have thought the returned value was int32_t, and simulator
cannot handle sign-extension of int32_t returned value implied by MIPS64 ABI
when execution is returned from C++ code.

[paul.l..., 2015-03-31 18:19:48]

The CQ bit was checked by paul.lind@imgtec.com

[commit-bot: I haz the power, 2015-03-31 18:20:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1040753003/1

[commit-bot: I haz the power, 2015-03-31 18:38:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-31 18:39:11]

Patchset 1 (id:??) landed as
https://crrev.com/5b760434814ade98f84aef8dd54e8c888f12de15
Cr-Commit-Position: refs/heads/master@{#27553}