Issue Description:

When the user declares a custom operator in the REPL, the operator is not defined in subsequent statements.

Steps to reproduce:

1. Open a terminal

2. Type in swift and press return to start the REPL

3. Type in postfix operator % and press return to declare an operator

4. Type in

postfix func %(value: Int) -> Int {
    value * 100
} 

and press return to define an implementation for this newly defined operator.

Expected results:

This should work

Actual results:

The following compiler error occurs:

error: repl.swift:11:14: error: operator implementation without matching operator declaration
postfix func %(value: Int) -> Int { 

Notes:

Any prefix, infix or postfix operator that is manually defined, is affected by this issue.

This issue is also reproducible in Swift Playgrounds if the operator declaration is executed separately from the implementation or call.