dillon1000/react

Remove ReactPropTypeLocationNames module

ReactPropTypeLocationNames was a map of location identifiers to location
display names, for use in warnings. But in practice, this did nothing
except rename "childContext" to "child context." Not worth it, IMO.

Since we are going to add an API for running prop type checks manually,
we need the ability to support arbitrary prop type locations. So
each place that used to accept a ReactPropTypeLocation now just accepts
a string.