Update index.d.ts

fixed backward compatibility

types/debug/index.d.ts

@@ -25,10 +25,14 @@ declare namespace debug {
 
         formatters: Formatters;
     }
+    
+    type IDebug=Debug;
 
     interface Formatters {
         [formatter: string]: (v: any) => string;
     }
+    
+    type IDebugger=Debugger;
 
     interface Debugger {
         (formatter: any, ...args: any[]): void;