Update to Flow 0.47

[iamdustan]

I was going to give rebasing #8545 a try and seeing what breaks, but first catching up to latest release of Flow. The big change here is that function call arity is now strictly enforces.

https://flow.org/blog/2017/05/07/Strict-Function-Call-Arity/

Specific call outs:

• Reverted flow’s understanding of getPooled and release variadic arguments with ...args: args
• The Fiber implementation was passing arguments through that were not used in a few places.
• ReactNative had a few issues with incomplete stubbed function typedefs. Fleshed those out enough for flow to be okay.
• ReactDOMFiber had an issue with {is: is} as the second arg to createElement. ignored it with $FlowIssue
• ReactDOMFiber every single createElement call was erroring because the entry string type was erroring when flowing into the more constrained types such as 'span' or 'th'|'td'. Got around it by changing the string type to the existential * type.

[acdlite]

Let's use mixed instead?

[iamdustan]

should I change all the anys to mixed?

[acdlite]

Yes please

[iamdustan]

Donesies.

[acdlite]

Also do you mind rebasing this on latest changes in master?

[iamdustan]

Note that debugging why CI was failing I realized that one of the hydration context APIs did require an argument. It was typedef’d as any which appears to have caused flow to think it was unused (or a PR changing it landed in the past day or so)

97ec4ca

[acdlite]

Thank you!