Make createScanner external (fixes #4057)

lib/typescriptServices.d.ts

@@ -1450,6 +1450,7 @@ declare namespace ts {
     function getTrailingCommentRanges(text: string, pos: number): CommentRange[];
     function isIdentifierStart(ch: number, languageVersion: ScriptTarget): boolean;
     function isIdentifierPart(ch: number, languageVersion: ScriptTarget): boolean;
+    function createScanner(languageVersion: ScriptTarget, skipTrivia: boolean, languageVariant: ts.LanguageVariant, text?: string, onError?: ErrorCallback, start?: number, length?: number): Scanner;
 }
 declare namespace ts {
     function getDefaultLibFileName(options: CompilerOptions): string;

src/compiler/scanner.ts

@@ -672,7 +672,6 @@ namespace ts {
             ch > CharacterCodes.maxAsciiCharacter && isUnicodeIdentifierPart(ch, languageVersion);
     }
 
-    /* @internal */
     // Creates a scanner over a (possibly unspecified) range of a piece of text.
     export function createScanner(languageVersion: ScriptTarget,
                                   skipTrivia: boolean,