Query, Explain and Cancel are going throught the asyncdbconnection now.

Todo: Notice processing and error reporting.

PgsqlConn.cpp

@@ -171,11 +171,15 @@ Canceller::~Canceller()
 	}
 }
 
-void Canceller::cancel()
+bool Canceller::cancel(std::string *error)
 {
 	const int errbuf_size = 256;
 	char errbuf[errbuf_size];
-	PQcancel(m_cancel, errbuf, errbuf_size);
+	bool res = PQcancel(m_cancel, errbuf, errbuf_size);
+	if (!res && error) {
+		*error = errbuf;
+	}
+	return res;
 }
 
 
@@ -272,11 +276,11 @@ bool Connection::sendQuery(const char *query)
 	return res == 1;
 }
 
-std::unique_ptr<Result> Connection::getResult()
+std::shared_ptr<Result> Connection::getResult()
 {
 	PGresult *r = PQgetResult(conn);
 	if (r) {
-		return std::make_unique<Result>(r);
+		return std::make_shared<Result>(r);
 	}
 	else {
 		return nullptr;