Added 'base' for 'gulp-watch' tests.

gulp/gulp.d.ts

@@ -28,6 +28,13 @@ declare module gulp {
          */
         buffer?: boolean;
 
+        /**
+         * The base path of a glob.
+         *
+         * Default is everything before a glob starts.
+         */
+        base?: string;
+
         /**
          * The current working directory in which to search.
          * Defaults to process.cwd().