Update to 31.3.0

Changelog:
Fixed Security fixes can be found here
Fixed @ JS::Handle::operator JSObject* const&() startup crash (see bug 1055766 )
Fixed Intermittent failures in add-ons manager mochitest-browser tests (see bug 1095128 )
Fixed Bad CPU type in executable running mochitests on yosemite (see bug 1054043 )
Fixed Error building nsChildView.mm on OS X 10.10 (see bug 1005458 )
Fixed Wrong CPU features detection on some x86 CPUs (see bug 1096651 )
Fixed Build error on Yosemite (see bug 1045231 )
Fixed XMLHttpRequest.send({}) should not throw (see bug 1096263 )

2014-90 Apple CoreGraphics framework on OS X 10.10 logging input data to /tmp directory
2014-89 Bad casting from the BasicThebesLayer to BasicContainerLayer
2014-88 Buffer overflow while parsing media content
2014-87 Use-after-free during HTML5 parsing
2014-85 XMLHttpRequest crashes with some input streams
2014-83 Miscellaneous memory safety hazards (rv:34.0 / rv:31.3)

(ryoon)