Moved function used in declaration emitter to the declaration emitter to break dependency loop.

src/compiler/declarationEmitter.ts

@@ -37,6 +37,10 @@ module ts {
         return diagnostics;
     }
 
+    export function isExternalModuleOrDeclarationFile(sourceFile: SourceFile) {
+        return isExternalModule(sourceFile) || isDeclarationFile(sourceFile);
+    }
+
     function emitDeclarations(host: EmitHost, resolver: EmitResolver, diagnostics: Diagnostic[], jsFilePath: string, root?: SourceFile): DeclarationEmit {
         let newLine = host.getNewLine();
         let compilerOptions = host.getCompilerOptions();

src/compiler/emitter.ts

@@ -3,10 +3,6 @@
 
 /* @internal */
 module ts {
-    export function isExternalModuleOrDeclarationFile(sourceFile: SourceFile) {
-        return isExternalModule(sourceFile) || isDeclarationFile(sourceFile);
-    }
-
     // Flags enum to track count of temp variables and a few dedicated names
     const enum TempFlags {
         Auto      = 0x00000000,  // No preferred name