fix(addon): cancel by c++ thread instead of nodejs thread

Segfaults were possible under conditions described in related issue

BREAKING CHANGE: cancel() method removed at addon level, remains on client and pool level

fix #234

lib/wrapper/noderfc-bindings.d.ts

@@ -28,10 +28,6 @@ export interface NWRfcBinding {
     environment: NodeRfcEnvironment;
     setIniFileDirectory(iniFileDirectory: string): any | undefined;
     loadCryptoLibrary(libAbsolutePath: string): any | undefined;
-    cancel(client: {
-        connectionHandle: number;
-        functionHandle?: number;
-    }, callback?: Function): any | undefined;
     verbose(): this;
 }
 declare let noderfc_binding: NWRfcBinding;

lib/wrapper/sapnwrfc-client.d.ts

@@ -73,6 +73,7 @@ export interface RfcClientBinding {
     close(callback: Function): void;
     resetServerContext(callback: Function): void;
     ping(callback: Function): void;
+    cancel(callback: Function): void;
     invoke(rfmName: string, rfmParams: RfcObject, callback: Function, callOptions?: RfcCallOptions): void;
     release(oneClientBinding: [RfcClientBinding], callback: Function): void;
 }
@@ -94,7 +95,7 @@ export declare class Client {
     open(callback?: Function): void | Promise<Client>;
     ping(callback?: Function): void | Promise<boolean>;
     close(callback?: Function): void | Promise<void>;
-    cancel(callback?: Function): void | Promise<any>;
+    cancel(callback?: Function): void | Promise<void>;
     resetServerContext(callback?: Function): void | Promise<void>;
     release(callback?: Function): void | Promise<void>;
     call(rfmName: string, rfmParams: RfcObject, callOptions?: RfcCallOptions): Promise<RfcObject>;