Reduce warnings noise when including wtf/Platform.h in KJS

[Stephen Kelly]

Aleix Pol Gonzalez wrote:

> This patch adds a defined() first, before checking the value, so the
> pre-processor doesn't need to consider the variable value, if it's not
> present.

This seems like a bad idea.

> These are defined with "1" if acceptable and undefined if the feature is 
> not present.

This is the problem that should be fixed. 

It should be 0 if the feature is not present. Please fix that instead.

Thanks,

Steve.