Fix Flow.

Removed `@flow` annotation from files that don't actually pass Flow check at the moment. These will be added back file by file once the files are properly converted to use Flow.

Closes #3064

src/util/identifier.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 // This is a trick taken from Esprima. It turns out that, on
 // non-Chrome browsers, to check whether a string is in a set, a
 // predicate containing a big ugly `switch` statement is faster than

src/util/location.js

@@ -1,5 +1,3 @@
-/* @flow */
-
 import { lineBreakG } from "./whitespace";
 
 // These are used when `options.locations` is on, for the

src/util/whitespace.js

@@ -6,7 +6,7 @@
 export const lineBreak = /\r\n?|\n|\u2028|\u2029/;
 export const lineBreakG = new RegExp(lineBreak.source, "g");
 
-export function isNewLine(code) {
+export function isNewLine(code: number): boolean {
   return code === 10 || code === 13 || code === 0x2028 || code === 0x2029;
 }