Add missing definition to shims

src/services/shims.ts

@@ -89,6 +89,7 @@ module ts {
         getCompilerOptionsDiagnostics(): string;
 
         getSyntacticClassifications(fileName: string, start: number, length: number): string;
+        getSemanticClassifications(fileName: string, start: number, length: number): string;
 
         getCompletionsAtPosition(fileName: string, position: number): string;
         getCompletionEntryDetails(fileName: string, position: number, entryName: string): string;