Make babel-register 7.x backward-compatible with 6.x. (#6268)

packages/babel-register/src/browser.js

@@ -1,3 +1,5 @@
 // required to safely use babel/register within a browserify codebase
 
-export default function() {}
+export default function register() {}
+
+export function revert() {}

packages/babel-register/src/index.js

@@ -0,0 +1,15 @@
+/**
+ * This file wraps the compiled ES6 module implementation of register so
+ * that it can be used both from a standard CommonJS environment, and also
+ * from a compiled Babel import.
+ */
+
+exports = module.exports = function(...args) {
+  return register(...args);
+};
+exports.__esModule = true;
+
+const node = require("./node");
+const register = node.default;
+
+Object.assign(exports, node);