dillon1000/react

[hir] Update mutable range of operands during LeaveSSA

It's not enough to only update the mutable range of the canonical id created 
instead of the phi but we need to update the mutable range of each of the 
operands of the phi as well to account for the fact that the phi could've been 
mutated later. 

The operands are updated only if the phi is mutated later. Otherwise these 
operands can be cached in their blocks. 

Fixes https://github.com/facebook/react-forget/issues/978