change PIIODevice read* and write* methods size to "ssize_t"

libs/main/io_devices/piserial.h

@@ -292,8 +292,8 @@ protected:
 
 	//! \~english Basic read function
 	//! \~russian Базовое чтение
-	int readDevice(void * read_to, int max_size) override;
-	int writeDevice(const void * data, int max_size) override;
+	ssize_t readDevice(void * read_to, ssize_t max_size) override;
+	ssize_t writeDevice(const void * data, ssize_t max_size) override;
 	DeviceInfoFlags deviceInfoFlags() const override {return PIIODevice::Sequential;}
 
 	//! Executes when any read function was successful. Default implementation does nothing