patch: 7_polling

An application that has own events and file descriptors, must poll select function ob libbsc. A "polling" flag is used to enable polling. In this case select() will not sleep until file descriptor events occurr or nearest timer expires. Also a return value will indicate if there was an event that has been handled. If there was an event, the application decides to poll again and don't wait. In case for bsc_hack, the polling flag is not set. select will sleep as usual.