Use version 1.7.3

Author: Yui T

src/compiler/program.ts

@@ -12,7 +12,7 @@ namespace ts {
 
     let emptyArray: any[] = [];
 
-    export const version = "1.7.2";
+    export const version = "1.7.3";
 
     export function findConfigFile(searchPath: string): string {
         let fileName = "tsconfig.json";