Redesign the FFI: don't use st_* functions from urweb
Add Callback.ur to the library; fix issues
Ur/Web compiler patch revisioned
Add more essential patches
Some enhancements

* Add createB function (takes blob as an argument)
* Read stdout as tail -f does
* Fix invalid 'select timeout' message
Add 'lastLineOfStdout' function
API changes, critical fixes

* add missing uw_begin_init call
* fix uw_malloc/uw_register_transactional order
* pass stdin with the run's argument