Update documentation for Function::call to reflect how 'this' behaves in non-strict mode
Update documentation for Function::call to reflect how 'this' behaves in non-strict mode

Summary: The `Function::call` method says it leaves the JS `this` object undefined. According to my tests, that's not completely true: if the function is defined to use strict mode via `"use strict"` either inside itself or in the file it was defined in, it does leave it `undefined`, but if the function is defined in non-strict mode, it sets `this` to the global object instead. This diff updates the documentation to reflect this.

Reviewed By: mhorowitz

Differential Revision: D19613483

fbshipit-source-id: 4b9ecf81c6318592be05a216748dcb22e32989f8

arthuralee/react-native,exponent/react-native,myntra/react-native,facebook/react-native,javache/react-native,exponent/react-native,hoangpham95/react-native,myntra/react-native,javache/react-native,hoangpham95/react-native,janicduplessis/react-native,facebook/react-native,pandiaraj44/react-native,myntra/react-native,exponent/react-native,hoangpham95/react-native,facebook/react-native,janicduplessis/react-native,exponent/react-native,facebook/react-native,facebook/react-native,exponentjs/react-native,hammerandchisel/react-native,facebook/react-native,exponentjs/react-native,myntra/react-native,javache/react-native,exponentjs/react-native,hoangpham95/react-native,arthuralee/react-native,pandiaraj44/react-native,exponentjs/react-native,myntra/react-native,janicduplessis/react-native,janicduplessis/react-native,javache/react-native,hammerandchisel/react-native,pandiaraj44/react-native,exponent/react-native,pandiaraj44/react-native,exponentjs/react-native,pandiaraj44/react-native,exponent/react-native,janicduplessis/react-native,hoangpham95/react-native,facebook/react-native,hammerandchisel/react-native,myntra/react-native,hoangpham95/react-native,javache/react-native,hammerandchisel/react-native,pandiaraj44/react-native,hoangpham95/react-native,exponentjs/react-native,pandiaraj44/react-native,facebook/react-native,exponentjs/react-native,hammerandchisel/react-native,hammerandchisel/react-native,exponent/react-native,janicduplessis/react-native,janicduplessis/react-native,arthuralee/react-native,exponentjs/react-native,hammerandchisel/react-native,exponent/react-native,javache/react-native,pandiaraj44/react-native,arthuralee/react-native,facebook/react-native,javache/react-native,myntra/react-native,hoangpham95/react-native,javache/react-native,myntra/react-native,janicduplessis/react-native,myntra/react-native,hammerandchisel/react-native,arthuralee/react-native,javache/react-native