fix(@angular-devkit/build-optimizer): deprecate transform test functions

These were not intended to be part of the public API and will eventually be removed completely.

Author: clydin

packages/angular_devkit/build_optimizer/src/transforms/import-tslib.ts

@@ -7,7 +7,9 @@
  */
 import * as ts from 'typescript';
 
-
+/**
+ * @deprecated From 0.9.0
+ */
 export function testImportTslib(content: string) {
   const regex = /var (__extends|__decorate|__metadata|__param) = \(.*\r?\n(    .*\r?\n)*\};/;
 

packages/angular_devkit/build_optimizer/src/transforms/prefix-classes.ts

@@ -7,7 +7,9 @@
  */
 import * as ts from 'typescript';
 
-
+/**
+ * @deprecated From 0.9.0
+ */
 export function testPrefixClasses(content: string) {
   const exportVarSetter = /(?:export )?(?:var|const)\s+(\S+)\s*=\s*/;
   const multiLineComment = /\s*(?:\/\*[\s\S]*?\*\/)?\s*/;

packages/angular_devkit/build_optimizer/src/transforms/scrub-file.ts

@@ -8,7 +8,9 @@
 import * as ts from 'typescript';
 import { collectDeepNodes } from '../helpers/ast-utils';
 
-
+/**
+ * @deprecated From 0.9.0
+ */
 export function testScrubFile(content: string) {
   const markers = [
     'decorators',