dillon1000/react

Allow prefixed hooks for compiling bundled code

We're doing some internal benchmarking using a lightweight bundler that @pieterv 
wrote for experimentation purposes. It's designed to fully preserve Flow type 
annotations so we can experiment with type-driven compilation and test out what 
benefits we might get from "cross-module" compilation more easily (ie by just 
bundling together a few modules so we can see them all as one). 

However, the bundler renames local variables and imports, so that a reference to 
`useMemo()` might end up as `React$useMemo()` or similar. This PR adds a flag to 
tell the compiler that builtin hooks might be prefixed and resolve them 
appropriately.