Negative zero checks cause unnecessary speculation failures on SunSpider on ARMv7...

Negative zero checks cause unnecessary speculation failures on SunSpider on ARMv7. (https://bugs.webkit.org/show_bug.cgi?id=113862)

[Title] Negative zero checks cause unnecessary speculation failures on SunSpider on ARMv7.
[Issue#] N/A
[Problem] While testing SunSpider math-spectral-norm on x86-64 and ARMv7 Linux,
          there are a lot of "Speculation failures" on ARM, but not on x86.
[Cause] N/A
[Solution] Check nodeCanIgnoreNegativeZero() for DoubleAsInt32 nodes, and create zero-check only when needed.

Change-Id: I50384d628a7ed8928d1378c52fe100f6de02197d