[MERGE #1350 @ThomsonTan] Avoid calling ::pow(double, int) in CRT which has a imprecision bug
[MERGE #1350 @ThomsonTan] Avoid calling ::pow(double, int) in CRT which has a imprecision bug

Merge pull request #1350 from ThomsonTan:FixMathPow

::pow(double, int) causes significant imprecision for exponents which is not very small. This is fixed in Visual Studio 2015 update 2 but haven't reached us. No side effect of avoid calling it since we optimize integer exponent in our side.

mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore